When millions of rods in our eyes are ...

Women’s minds work differently from men’s. At least, that is what most men are convinced of. Psychologists view the subject either as a matter of frustration or a joke. Now the biologists have moved into this minefield, and some of them have found that there are real differences between the brains of men and women. But being different, they point out hurriedly, is not the same as being better or worse. There is, however, a definite structural variation between the male and female brain. The difference is in a part of the brain that is used in the most complex intellectual processes — the link between the two halves of the brain. The two halves are linked by a trunk line of between 200 and 300 million nerves, the corpus callosum (胼胝体) . Scientists have found quite recently that the corpus callosum in women is always larger and probably richer in nerve fibers than it is in men. This is the first time that a structural difference has been found between the brains of women and men and it must have some significance. The question is "What", and, if this difference exists, are there others Research shows that present-day women think differently and behave differently from men. Are some of these differences biological and inborn, a result of evolution We tend to think that is the influence of society that produces these differences. But could we be wrong Research showed that these two halves of the brain had different functions, and that the corpus callosum enabled them to work together. For most people, the left half is used for word-handing, analytical and logical activities; the right half works on pictures, patterns and forms. We need both halves working together. And the better the connections, the more harmoniously the two halves work. And, according to research findings, women have the better connections. But it isn’t all that easy to explain the actual differences between skills of men and women on this basis. In schools throughout the world girls tend to be better than boys at "language subjects" and boys better at maths and physics. If these differences correspond with the differences in the hemispheric trunk line, there is an unalterable distinction between the sexes. We shan’t know for a while, partly because we don’t know of any precise relationship between abilities in school subject and the functioning of the two halves of the brain, and we cannot understand how the two halves interact via the corpus callosum. But this striking difference must have some effect and, because the difference is in the parts of the brain involved in intellect, we should be looking for differences in intellectual processing.Which of the following statement is CORRECT

A．Biologists are conducting research where psychologists have given up.
B．Main differences point to superiority of one sex over the other.
C．Results of scientific research fail to support popular belief.
D．The structural difference in the brain between the sexes has long been known.

单项选择题

Women’s minds work differently from men’s. At least, that is what most men are convinced of. Psychologists view the subject either as a matter of frustration or a joke. Now the biologists have moved into this minefield, and some of them have found that there are real differences between the brains of men and women. But being different, they point out hurriedly, is not the same as being better or worse. There is, however, a definite structural variation between the male and female brain. The difference is in a part of the brain that is used in the most complex intellectual processes — the link between the two halves of the brain. The two halves are linked by a trunk line of between 200 and 300 million nerves, the corpus callosum (胼胝体) . Scientists have found quite recently that the corpus callosum in women is always larger and probably richer in nerve fibers than it is in men. This is the first time that a structural difference has been found between the brains of women and men and it must have some significance. The question is "What", and, if this difference exists, are there others Research shows that present-day women think differently and behave differently from men. Are some of these differences biological and inborn, a result of evolution We tend to think that is the influence of society that produces these differences. But could we be wrong Research showed that these two halves of the brain had different functions, and that the corpus callosum enabled them to work together. For most people, the left half is used for word-handing, analytical and logical activities; the right half works on pictures, patterns and forms. We need both halves working together. And the better the connections, the more harmoniously the two halves work. And, according to research findings, women have the better connections. But it isn’t all that easy to explain the actual differences between skills of men and women on this basis. In schools throughout the world girls tend to be better than boys at "language subjects" and boys better at maths and physics. If these differences correspond with the differences in the hemispheric trunk line, there is an unalterable distinction between the sexes. We shan’t know for a while, partly because we don’t know of any precise relationship between abilities in school subject and the functioning of the two halves of the brain, and we cannot understand how the two halves interact via the corpus callosum. But this striking difference must have some effect and, because the difference is in the parts of the brain involved in intellect, we should be looking for differences in intellectual processing.According to the passage it is commonly believed that brain differences are caused by_____factors.

A．biological
B．psychological
C．physical
D．social

单项选择题

Women’s minds work differently from men’s. At least, that is what most men are convinced of. Psychologists view the subject either as a matter of frustration or a joke. Now the biologists have moved into this minefield, and some of them have found that there are real differences between the brains of men and women. But being different, they point out hurriedly, is not the same as being better or worse. There is, however, a definite structural variation between the male and female brain. The difference is in a part of the brain that is used in the most complex intellectual processes — the link between the two halves of the brain. The two halves are linked by a trunk line of between 200 and 300 million nerves, the corpus callosum (胼胝体) . Scientists have found quite recently that the corpus callosum in women is always larger and probably richer in nerve fibers than it is in men. This is the first time that a structural difference has been found between the brains of women and men and it must have some significance. The question is "What", and, if this difference exists, are there others Research shows that present-day women think differently and behave differently from men. Are some of these differences biological and inborn, a result of evolution We tend to think that is the influence of society that produces these differences. But could we be wrong Research showed that these two halves of the brain had different functions, and that the corpus callosum enabled them to work together. For most people, the left half is used for word-handing, analytical and logical activities; the right half works on pictures, patterns and forms. We need both halves working together. And the better the connections, the more harmoniously the two halves work. And, according to research findings, women have the better connections. But it isn’t all that easy to explain the actual differences between skills of men and women on this basis. In schools throughout the world girls tend to be better than boys at "language subjects" and boys better at maths and physics. If these differences correspond with the differences in the hemispheric trunk line, there is an unalterable distinction between the sexes. We shan’t know for a while, partly because we don’t know of any precise relationship between abilities in school subject and the functioning of the two halves of the brain, and we cannot understand how the two halves interact via the corpus callosum. But this striking difference must have some effect and, because the difference is in the parts of the brain involved in intellect, we should be looking for differences in intellectual processing." These differences" in Paragraph 5 refer to those in_____.

A．skills of men and women
B．school subjects
C．the brain structure of men and women
D．activities carried out by the brain

单项选择题

Women’s minds work differently from men’s. At least, that is what most men are convinced of. Psychologists view the subject either as a matter of frustration or a joke. Now the biologists have moved into this minefield, and some of them have found that there are real differences between the brains of men and women. But being different, they point out hurriedly, is not the same as being better or worse. There is, however, a definite structural variation between the male and female brain. The difference is in a part of the brain that is used in the most complex intellectual processes — the link between the two halves of the brain. The two halves are linked by a trunk line of between 200 and 300 million nerves, the corpus callosum (胼胝体) . Scientists have found quite recently that the corpus callosum in women is always larger and probably richer in nerve fibers than it is in men. This is the first time that a structural difference has been found between the brains of women and men and it must have some significance. The question is "What", and, if this difference exists, are there others Research shows that present-day women think differently and behave differently from men. Are some of these differences biological and inborn, a result of evolution We tend to think that is the influence of society that produces these differences. But could we be wrong Research showed that these two halves of the brain had different functions, and that the corpus callosum enabled them to work together. For most people, the left half is used for word-handing, analytical and logical activities; the right half works on pictures, patterns and forms. We need both halves working together. And the better the connections, the more harmoniously the two halves work. And, according to research findings, women have the better connections. But it isn’t all that easy to explain the actual differences between skills of men and women on this basis. In schools throughout the world girls tend to be better than boys at "language subjects" and boys better at maths and physics. If these differences correspond with the differences in the hemispheric trunk line, there is an unalterable distinction between the sexes. We shan’t know for a while, partly because we don’t know of any precise relationship between abilities in school subject and the functioning of the two halves of the brain, and we cannot understand how the two halves interact via the corpus callosum. But this striking difference must have some effect and, because the difference is in the parts of the brain involved in intellect, we should be looking for differences in intellectual processing.At the end of the passage the author proposes more work on______.

A．the brain structure as a whole
B．the functioning of part of the brain
C．the distinction between the sexes
D．the effects of the corpus callosum

单项选择题

Women’s minds work differently from men’s. At least, that is what most men are convinced of. Psychologists view the subject either as a matter of frustration or a joke. Now the biologists have moved into this minefield, and some of them have found that there are real differences between the brains of men and women. But being different, they point out hurriedly, is not the same as being better or worse. There is, however, a definite structural variation between the male and female brain. The difference is in a part of the brain that is used in the most complex intellectual processes — the link between the two halves of the brain. The two halves are linked by a trunk line of between 200 and 300 million nerves, the corpus callosum (胼胝体) . Scientists have found quite recently that the corpus callosum in women is always larger and probably richer in nerve fibers than it is in men. This is the first time that a structural difference has been found between the brains of women and men and it must have some significance. The question is "What", and, if this difference exists, are there others Research shows that present-day women think differently and behave differently from men. Are some of these differences biological and inborn, a result of evolution We tend to think that is the influence of society that produces these differences. But could we be wrong Research showed that these two halves of the brain had different functions, and that the corpus callosum enabled them to work together. For most people, the left half is used for word-handing, analytical and logical activities; the right half works on pictures, patterns and forms. We need both halves working together. And the better the connections, the more harmoniously the two halves work. And, according to research findings, women have the better connections. But it isn’t all that easy to explain the actual differences between skills of men and women on this basis. In schools throughout the world girls tend to be better than boys at "language subjects" and boys better at maths and physics. If these differences correspond with the differences in the hemispheric trunk line, there is an unalterable distinction between the sexes. We shan’t know for a while, partly because we don’t know of any precise relationship between abilities in school subject and the functioning of the two halves of the brain, and we cannot understand how the two halves interact via the corpus callosum. But this striking difference must have some effect and, because the difference is in the parts of the brain involved in intellect, we should be looking for differences in intellectual processing.What is the main purpose of the passage

A．To outline the research findings on the brain structure.
B．To explain the link between sex and brain structure.
C．To discuss the various factors that cause brain differences.
D．To suggest new areas in brain research.

单项选择题

Can electricity cause cancer In a society that literally runs on electric power, the very idea seems preposterous. But for more than a decade, a growing band of scientists and journalists has pointed to studies that seem to link exposure to electromagnetic fields with increased risk of leukemia and other malignancies. The implications are unsettling, to say the least, since everyone comes into contact with such fields, which are generated by everything electrical, from power lines and antennas to personal computers and micro-wave ovens. Because evidence on the subject is inconclusive and often contradictory, it has been hard to decide whether concern about the health effects of electricity is legitimate—or the worst kind of paranoia. Now the alarmists have gained some qualified support from the U. S. Environmental Protection Agency. In the executive summary of a new scientific review, released in draft form late last week, the EPA has put forward what amounts to the most serious government warning to date. The agency tentatively concludes that scientific evidence "suggests a casual link" between extremely low-frequency electromagnetic fields — those having very longwave-lengths — and leukemia, lymphoma and brain cancer, While the report falls short of classifying ELF fields as probable carcinogens, it does identify the common 60-hertz magnetic field as "a possible, but not proven, cause of cancer in humans". The report is no reason to panic—or even to lost sleep. If there is a cancer risk, it is a small one. The evidence is still so controversial that the draft stirred a great deal of debate within the Bush Administration, and the EPA released it over strong objections from the Pentagon and the White House. But now no one can deny that the issue must be taken seriously and that much more research is needed. At the heart of the debate is a simple and well-understood physical phenomenon: When an electric current passes through a wire, it generates an electromagnetic field that exerts forces on surrounding objects. For many years, scientists dismissed any suggestion that such forces might be harmful, primarily because they are so extraordinarily weak. The ELF magnetic field generated by a video terminal measures only a few milligauss, or about one-hundredth the strength of the earth’s own magnetic field. The electric fields surrounding a power line can be as high as 10 kilovolts per meter, but the corresponding field induced in human cells will be only about 1 millivolt per meter. This is far less than the electric fields that the cells themselves generate. How could such minuscule forces pose a health danger The consensus used to be that they could not, and for decades scientists concentrated on more powerful kinds of radiation, like X-rays, that pack sufficient wallop to knock electrons out of the molecules that make up the human body. Such "ionizing" radiations have been clearly linked to increased cancer risks and there are regulations to control emissions. But epidemiological studies, which find statistical associations between sets of data, do not prove cause and effect. Though there is a body of laboratory work showing that exposure to ELF fields can have biological effects on animal tissues, a mechanism by which those effects could lead to cancerous growths has never been found. The Pentagon is far from persuaded. In a blistering 33-page critique of the EPA report, Air Force scientists charge its authors with having "biased the entire document" toward proving a link. "Our reviewers are convinced that there is no suggestion that electromagnetic fields present in the environment induce or promote cancer, " the Air Force concludes. "It is astonishing that the EPA would lend its imprimatur on this report. " Then Pentagon’s concern is understandable. There is hardly a unit of the modern military that does not depend on the heavy use of some kind of electronic equipment, from huge ground-based radar towers to the defense systems built into every warship and plane.The main idea of this passage is______.

A．studies on the cause of cancer
B．controversial view-points in the cause of cancer
C．the relationship between electricity and cancer
D．different ideas about the effect of electricity on cancer

单项选择题

Here’s a familiar version of the boy-meets-girl situation. A young man has at last plucked up courage to invite a dazzling young lady out to dinner. She has accepted his invitation and he is overjoyed. He is determined to take her to the best restaurant in town, even if it means that he will have to live on memories and hopes during the month to come. When they get to the restaurant, he discovers that this ethereal creature is on a diet. She mustn’t eat this and she mustn’t eat that. Oh, but of course, she doesn’t want to spoil his enjoyment. Let him by all means eat as much fattening food as he wants: it’s the surest way to an early grave. They spend a truly memorable evening together and never see each other again. What a miserable lot dieters are! You can always recognize them from the sour expression on their faces. They spend most of their time turning their noses up at food. They are forever consulting calorie charts; gazing at themselves in mirrors; and leaping on to weighing-machines in the bathroom. They spend a lifetime fighting a losing battle against spreading hips, protruding tummies and double chins. Some wage all-out war on FAT. Mere dieting is not enough. They exhaust themselves doing exercises, sweating in sauna baths, being pummeled and massaged by weird machines. The really wealthy diet-mongers pay vast sums for "health cures". For two weeks they can enter a nature clinic and be starved to death for a hundred guineas a week. Don’t think it’s only the middle-aged who go in for these fads either. Many of these bright young things you see are suffering from chronic malnutrition: they are living on nothing but air, water and the goodwill of God. Dieters undertake to starve themselves of their own free will; so why are they so miserable Well, for one thing, they’re always hungry. You can’t be hungry and happy at the same time. All the horrible concoctions they eat instead of food leave them permanently dissatisfied. Wonderfood is a complete food, the advertisement says. Just dissolve a teaspoonful in water. A complete food it may be, but not quite as complete as a juicy steak. And, of course, they’re always miserable because they feel so guilty. Hunger just proves too much for them and in the end they lash out and devour five huge guilt-inducing cream cakes at a sitting. And who can blame them At least three times a day they are exposed to temptation. What utter torture it is always watching others tucking into piles of mouth-watering food while you munch a water biscuit and sip unsweetened lemon juice! What’s all this self-inflicted torture for Saintly people deprive themselves of food to attain a state of grace. Unsaintly people do so to attain a state of misery. It will be a great day when all the dieters in the world abandon their slimming courses; when they hold out their plates and demand second helpings!The best title for this passage is______.

A．On Fat
B．We Should All Grow Fat and Be Happy
C．Many Diseases Are Connected with Fat
D．Diet Deprives People of Normal Life

单项选择题

Can electricity cause cancer In a society that literally runs on electric power, the very idea seems preposterous. But for more than a decade, a growing band of scientists and journalists has pointed to studies that seem to link exposure to electromagnetic fields with increased risk of leukemia and other malignancies. The implications are unsettling, to say the least, since everyone comes into contact with such fields, which are generated by everything electrical, from power lines and antennas to personal computers and micro-wave ovens. Because evidence on the subject is inconclusive and often contradictory, it has been hard to decide whether concern about the health effects of electricity is legitimate—or the worst kind of paranoia. Now the alarmists have gained some qualified support from the U. S. Environmental Protection Agency. In the executive summary of a new scientific review, released in draft form late last week, the EPA has put forward what amounts to the most serious government warning to date. The agency tentatively concludes that scientific evidence "suggests a casual link" between extremely low-frequency electromagnetic fields — those having very longwave-lengths — and leukemia, lymphoma and brain cancer, While the report falls short of classifying ELF fields as probable carcinogens, it does identify the common 60-hertz magnetic field as "a possible, but not proven, cause of cancer in humans". The report is no reason to panic—or even to lost sleep. If there is a cancer risk, it is a small one. The evidence is still so controversial that the draft stirred a great deal of debate within the Bush Administration, and the EPA released it over strong objections from the Pentagon and the White House. But now no one can deny that the issue must be taken seriously and that much more research is needed. At the heart of the debate is a simple and well-understood physical phenomenon: When an electric current passes through a wire, it generates an electromagnetic field that exerts forces on surrounding objects. For many years, scientists dismissed any suggestion that such forces might be harmful, primarily because they are so extraordinarily weak. The ELF magnetic field generated by a video terminal measures only a few milligauss, or about one-hundredth the strength of the earth’s own magnetic field. The electric fields surrounding a power line can be as high as 10 kilovolts per meter, but the corresponding field induced in human cells will be only about 1 millivolt per meter. This is far less than the electric fields that the cells themselves generate. How could such minuscule forces pose a health danger The consensus used to be that they could not, and for decades scientists concentrated on more powerful kinds of radiation, like X-rays, that pack sufficient wallop to knock electrons out of the molecules that make up the human body. Such "ionizing" radiations have been clearly linked to increased cancer risks and there are regulations to control emissions. But epidemiological studies, which find statistical associations between sets of data, do not prove cause and effect. Though there is a body of laboratory work showing that exposure to ELF fields can have biological effects on animal tissues, a mechanism by which those effects could lead to cancerous growths has never been found. The Pentagon is far from persuaded. In a blistering 33-page critique of the EPA report, Air Force scientists charge its authors with having "biased the entire document" toward proving a link. "Our reviewers are convinced that there is no suggestion that electromagnetic fields present in the environment induce or promote cancer, " the Air Force concludes. "It is astonishing that the EPA would lend its imprimatur on this report. " Then Pentagon’s concern is understandable. There is hardly a unit of the modern military that does not depend on the heavy use of some kind of electronic equipment, from huge ground-based radar towers to the defense systems built into every warship and plane.The view-point of the EPA is______.

A．there is casual link between electricity and cancer
B．electricity really affects cancer
C．controversial
D．low frequency electromagnetic field is a possible cause of cancer

单项选择题

Here’s a familiar version of the boy-meets-girl situation. A young man has at last plucked up courage to invite a dazzling young lady out to dinner. She has accepted his invitation and he is overjoyed. He is determined to take her to the best restaurant in town, even if it means that he will have to live on memories and hopes during the month to come. When they get to the restaurant, he discovers that this ethereal creature is on a diet. She mustn’t eat this and she mustn’t eat that. Oh, but of course, she doesn’t want to spoil his enjoyment. Let him by all means eat as much fattening food as he wants: it’s the surest way to an early grave. They spend a truly memorable evening together and never see each other again. What a miserable lot dieters are! You can always recognize them from the sour expression on their faces. They spend most of their time turning their noses up at food. They are forever consulting calorie charts; gazing at themselves in mirrors; and leaping on to weighing-machines in the bathroom. They spend a lifetime fighting a losing battle against spreading hips, protruding tummies and double chins. Some wage all-out war on FAT. Mere dieting is not enough. They exhaust themselves doing exercises, sweating in sauna baths, being pummeled and massaged by weird machines. The really wealthy diet-mongers pay vast sums for "health cures". For two weeks they can enter a nature clinic and be starved to death for a hundred guineas a week. Don’t think it’s only the middle-aged who go in for these fads either. Many of these bright young things you see are suffering from chronic malnutrition: they are living on nothing but air, water and the goodwill of God. Dieters undertake to starve themselves of their own free will; so why are they so miserable Well, for one thing, they’re always hungry. You can’t be hungry and happy at the same time. All the horrible concoctions they eat instead of food leave them permanently dissatisfied. Wonderfood is a complete food, the advertisement says. Just dissolve a teaspoonful in water. A complete food it may be, but not quite as complete as a juicy steak. And, of course, they’re always miserable because they feel so guilty. Hunger just proves too much for them and in the end they lash out and devour five huge guilt-inducing cream cakes at a sitting. And who can blame them At least three times a day they are exposed to temptation. What utter torture it is always watching others tucking into piles of mouth-watering food while you munch a water biscuit and sip unsweetened lemon juice! What’s all this self-inflicted torture for Saintly people deprive themselves of food to attain a state of grace. Unsaintly people do so to attain a state of misery. It will be a great day when all the dieters in the world abandon their slimming courses; when they hold out their plates and demand second helpings!Why do they never see each other again

A．Because it is a memorable evening.
B．Because she lets him eat as much fattening food as he wants.
C．Because she does not eat this and drink that.
D．Because eating fattening food is the surest way to an early grave.

单项选择题

For three decades we’ve heard endlessly about the virtues of aerobic (increasing oxygen consumption) exercise. Medical authorities have praised running and jumping as the key to good health, and millions of Americans have taken to the treadmill to reap the rewards. But the story is changing. Everyone from the American Heart Association to the surgeon general’s office has recently embraced strength training as a complement to aerobics. And as weight lifting has gone mainstream, so has the once obscure practice known as "Super Slow" training. Enthusiasts claim that by pumping iron at a snail’s pace — making each "rep" (repeat) last 14 seconds instead of the usual 7 — you can safely place extraordinary demands on your muscles, and call forth an extraordinary response. Slow lifting may not be the only exercise you need, as some advocates believe, but the benefits are often dramatic. Almost anyone can handle this routine. The only requirements are complete focus and a tolerance for deep muscular burn. For each exercise — leg press, bench press, shoulder press and so on — you set the machine to provide only moderate resistance. But as you draw out each repeat, depriving yourself of impetus, the weight soon feels unbearable. Defying the impulse to stop, you kept going until you can’t complete a repeat. Then you sustain your vain effort for 10 more seconds while the weight sinks gradually toward its cradle. Intense Uncomfortable Totally. But once you embrace muscle failure as the goal of the workout, it can become almost pleasure. The goal is not to burn calories while you’re exercising but to make your body burn them all the time. Running a few miles may make you sweat, but it expends only 100 calories per mile, and it doesn’t stimulate much bone or muscle development. Strength training doesn’t burn many calories, either. But when you push a muscle to failure, you set off a pour of physiological changes. As the muscle recovers over several days, it will thicken — and the new muscle tissue will demand sustenance. By the time you add three pounds of muscle, your body requires an extra 9, 000 calories a month just to break even. Hold your diet steady and, very quickly, you are vaporizing body fat. One might have benefited from any strength-training program. But advocates insist the slow technique is safer and more effective than traditional methods.Many Americans have taken to treadmill for______.

A．its inherent awards to their health
B．its greater consumption of oxygen
C．the compliment paid by authorities
D．the actual benefits from the exercise

单项选择题

Can electricity cause cancer In a society that literally runs on electric power, the very idea seems preposterous. But for more than a decade, a growing band of scientists and journalists has pointed to studies that seem to link exposure to electromagnetic fields with increased risk of leukemia and other malignancies. The implications are unsettling, to say the least, since everyone comes into contact with such fields, which are generated by everything electrical, from power lines and antennas to personal computers and micro-wave ovens. Because evidence on the subject is inconclusive and often contradictory, it has been hard to decide whether concern about the health effects of electricity is legitimate—or the worst kind of paranoia. Now the alarmists have gained some qualified support from the U. S. Environmental Protection Agency. In the executive summary of a new scientific review, released in draft form late last week, the EPA has put forward what amounts to the most serious government warning to date. The agency tentatively concludes that scientific evidence "suggests a casual link" between extremely low-frequency electromagnetic fields — those having very longwave-lengths — and leukemia, lymphoma and brain cancer, While the report falls short of classifying ELF fields as probable carcinogens, it does identify the common 60-hertz magnetic field as "a possible, but not proven, cause of cancer in humans". The report is no reason to panic—or even to lost sleep. If there is a cancer risk, it is a small one. The evidence is still so controversial that the draft stirred a great deal of debate within the Bush Administration, and the EPA released it over strong objections from the Pentagon and the White House. But now no one can deny that the issue must be taken seriously and that much more research is needed. At the heart of the debate is a simple and well-understood physical phenomenon: When an electric current passes through a wire, it generates an electromagnetic field that exerts forces on surrounding objects. For many years, scientists dismissed any suggestion that such forces might be harmful, primarily because they are so extraordinarily weak. The ELF magnetic field generated by a video terminal measures only a few milligauss, or about one-hundredth the strength of the earth’s own magnetic field. The electric fields surrounding a power line can be as high as 10 kilovolts per meter, but the corresponding field induced in human cells will be only about 1 millivolt per meter. This is far less than the electric fields that the cells themselves generate. How could such minuscule forces pose a health danger The consensus used to be that they could not, and for decades scientists concentrated on more powerful kinds of radiation, like X-rays, that pack sufficient wallop to knock electrons out of the molecules that make up the human body. Such "ionizing" radiations have been clearly linked to increased cancer risks and there are regulations to control emissions. But epidemiological studies, which find statistical associations between sets of data, do not prove cause and effect. Though there is a body of laboratory work showing that exposure to ELF fields can have biological effects on animal tissues, a mechanism by which those effects could lead to cancerous growths has never been found. The Pentagon is far from persuaded. In a blistering 33-page critique of the EPA report, Air Force scientists charge its authors with having "biased the entire document" toward proving a link. "Our reviewers are convinced that there is no suggestion that electromagnetic fields present in the environment induce or promote cancer, " the Air Force concludes. "It is astonishing that the EPA would lend its imprimatur on this report. " Then Pentagon’s concern is understandable. There is hardly a unit of the modern military that does not depend on the heavy use of some kind of electronic equipment, from huge ground-based radar towers to the defense systems built into every warship and plane.Why did the Pentagon and White House object to the release of the report Because_____.

A．it may stir a great deal of debate among the Bush Administration
B．every unit of the modern military has depended on the heavy use of some kind of electronic equipment
C．the Pentagon’s concern was understandable
D．they had different arguments

单项选择题

For three decades we’ve heard endlessly about the virtues of aerobic (increasing oxygen consumption) exercise. Medical authorities have praised running and jumping as the key to good health, and millions of Americans have taken to the treadmill to reap the rewards. But the story is changing. Everyone from the American Heart Association to the surgeon general’s office has recently embraced strength training as a complement to aerobics. And as weight lifting has gone mainstream, so has the once obscure practice known as "Super Slow" training. Enthusiasts claim that by pumping iron at a snail’s pace — making each "rep" (repeat) last 14 seconds instead of the usual 7 — you can safely place extraordinary demands on your muscles, and call forth an extraordinary response. Slow lifting may not be the only exercise you need, as some advocates believe, but the benefits are often dramatic. Almost anyone can handle this routine. The only requirements are complete focus and a tolerance for deep muscular burn. For each exercise — leg press, bench press, shoulder press and so on — you set the machine to provide only moderate resistance. But as you draw out each repeat, depriving yourself of impetus, the weight soon feels unbearable. Defying the impulse to stop, you kept going until you can’t complete a repeat. Then you sustain your vain effort for 10 more seconds while the weight sinks gradually toward its cradle. Intense Uncomfortable Totally. But once you embrace muscle failure as the goal of the workout, it can become almost pleasure. The goal is not to burn calories while you’re exercising but to make your body burn them all the time. Running a few miles may make you sweat, but it expends only 100 calories per mile, and it doesn’t stimulate much bone or muscle development. Strength training doesn’t burn many calories, either. But when you push a muscle to failure, you set off a pour of physiological changes. As the muscle recovers over several days, it will thicken — and the new muscle tissue will demand sustenance. By the time you add three pounds of muscle, your body requires an extra 9, 000 calories a month just to break even. Hold your diet steady and, very quickly, you are vaporizing body fat. One might have benefited from any strength-training program. But advocates insist the slow technique is safer and more effective than traditional methods.According to the author, Super Slow training______.

A．has been misunderstood for decades
B．has been widely accepted recently
C．has been the basis of weight lifting
D．has become the nucleus of aerobics

单项选择题

Here’s a familiar version of the boy-meets-girl situation. A young man has at last plucked up courage to invite a dazzling young lady out to dinner. She has accepted his invitation and he is overjoyed. He is determined to take her to the best restaurant in town, even if it means that he will have to live on memories and hopes during the month to come. When they get to the restaurant, he discovers that this ethereal creature is on a diet. She mustn’t eat this and she mustn’t eat that. Oh, but of course, she doesn’t want to spoil his enjoyment. Let him by all means eat as much fattening food as he wants: it’s the surest way to an early grave. They spend a truly memorable evening together and never see each other again. What a miserable lot dieters are! You can always recognize them from the sour expression on their faces. They spend most of their time turning their noses up at food. They are forever consulting calorie charts; gazing at themselves in mirrors; and leaping on to weighing-machines in the bathroom. They spend a lifetime fighting a losing battle against spreading hips, protruding tummies and double chins. Some wage all-out war on FAT. Mere dieting is not enough. They exhaust themselves doing exercises, sweating in sauna baths, being pummeled and massaged by weird machines. The really wealthy diet-mongers pay vast sums for "health cures". For two weeks they can enter a nature clinic and be starved to death for a hundred guineas a week. Don’t think it’s only the middle-aged who go in for these fads either. Many of these bright young things you see are suffering from chronic malnutrition: they are living on nothing but air, water and the goodwill of God. Dieters undertake to starve themselves of their own free will; so why are they so miserable Well, for one thing, they’re always hungry. You can’t be hungry and happy at the same time. All the horrible concoctions they eat instead of food leave them permanently dissatisfied. Wonderfood is a complete food, the advertisement says. Just dissolve a teaspoonful in water. A complete food it may be, but not quite as complete as a juicy steak. And, of course, they’re always miserable because they feel so guilty. Hunger just proves too much for them and in the end they lash out and devour five huge guilt-inducing cream cakes at a sitting. And who can blame them At least three times a day they are exposed to temptation. What utter torture it is always watching others tucking into piles of mouth-watering food while you munch a water biscuit and sip unsweetened lemon juice! What’s all this self-inflicted torture for Saintly people deprive themselves of food to attain a state of grace. Unsaintly people do so to attain a state of misery. It will be a great day when all the dieters in the world abandon their slimming courses; when they hold out their plates and demand second helpings!What’s the meaning of "lot" in the first line of Paragraph 2

A．Amount.
B．Field.
C．Fate.
D．Group.

单项选择题

Can electricity cause cancer In a society that literally runs on electric power, the very idea seems preposterous. But for more than a decade, a growing band of scientists and journalists has pointed to studies that seem to link exposure to electromagnetic fields with increased risk of leukemia and other malignancies. The implications are unsettling, to say the least, since everyone comes into contact with such fields, which are generated by everything electrical, from power lines and antennas to personal computers and micro-wave ovens. Because evidence on the subject is inconclusive and often contradictory, it has been hard to decide whether concern about the health effects of electricity is legitimate—or the worst kind of paranoia. Now the alarmists have gained some qualified support from the U. S. Environmental Protection Agency. In the executive summary of a new scientific review, released in draft form late last week, the EPA has put forward what amounts to the most serious government warning to date. The agency tentatively concludes that scientific evidence "suggests a casual link" between extremely low-frequency electromagnetic fields — those having very longwave-lengths — and leukemia, lymphoma and brain cancer, While the report falls short of classifying ELF fields as probable carcinogens, it does identify the common 60-hertz magnetic field as "a possible, but not proven, cause of cancer in humans". The report is no reason to panic—or even to lost sleep. If there is a cancer risk, it is a small one. The evidence is still so controversial that the draft stirred a great deal of debate within the Bush Administration, and the EPA released it over strong objections from the Pentagon and the White House. But now no one can deny that the issue must be taken seriously and that much more research is needed. At the heart of the debate is a simple and well-understood physical phenomenon: When an electric current passes through a wire, it generates an electromagnetic field that exerts forces on surrounding objects. For many years, scientists dismissed any suggestion that such forces might be harmful, primarily because they are so extraordinarily weak. The ELF magnetic field generated by a video terminal measures only a few milligauss, or about one-hundredth the strength of the earth’s own magnetic field. The electric fields surrounding a power line can be as high as 10 kilovolts per meter, but the corresponding field induced in human cells will be only about 1 millivolt per meter. This is far less than the electric fields that the cells themselves generate. How could such minuscule forces pose a health danger The consensus used to be that they could not, and for decades scientists concentrated on more powerful kinds of radiation, like X-rays, that pack sufficient wallop to knock electrons out of the molecules that make up the human body. Such "ionizing" radiations have been clearly linked to increased cancer risks and there are regulations to control emissions. But epidemiological studies, which find statistical associations between sets of data, do not prove cause and effect. Though there is a body of laboratory work showing that exposure to ELF fields can have biological effects on animal tissues, a mechanism by which those effects could lead to cancerous growths has never been found. The Pentagon is far from persuaded. In a blistering 33-page critique of the EPA report, Air Force scientists charge its authors with having "biased the entire document" toward proving a link. "Our reviewers are convinced that there is no suggestion that electromagnetic fields present in the environment induce or promote cancer, " the Air Force concludes. "It is astonishing that the EPA would lend its imprimatur on this report. " Then Pentagon’s concern is understandable. There is hardly a unit of the modern military that does not depend on the heavy use of some kind of electronic equipment, from huge ground-based radar towers to the defense systems built into every warship and plane.It can be inferred from physical phenomenon______.

A．the force of the electromagnetic field is too weak to be harmful
B．the force of the electromagnetic field is weaker than the electric field that the cells generate
C．electromagnetic field may affect health
D．only more powerful radiation can knock electron out of human body

单项选择题

For three decades we’ve heard endlessly about the virtues of aerobic (increasing oxygen consumption) exercise. Medical authorities have praised running and jumping as the key to good health, and millions of Americans have taken to the treadmill to reap the rewards. But the story is changing. Everyone from the American Heart Association to the surgeon general’s office has recently embraced strength training as a complement to aerobics. And as weight lifting has gone mainstream, so has the once obscure practice known as "Super Slow" training. Enthusiasts claim that by pumping iron at a snail’s pace — making each "rep" (repeat) last 14 seconds instead of the usual 7 — you can safely place extraordinary demands on your muscles, and call forth an extraordinary response. Slow lifting may not be the only exercise you need, as some advocates believe, but the benefits are often dramatic. Almost anyone can handle this routine. The only requirements are complete focus and a tolerance for deep muscular burn. For each exercise — leg press, bench press, shoulder press and so on — you set the machine to provide only moderate resistance. But as you draw out each repeat, depriving yourself of impetus, the weight soon feels unbearable. Defying the impulse to stop, you kept going until you can’t complete a repeat. Then you sustain your vain effort for 10 more seconds while the weight sinks gradually toward its cradle. Intense Uncomfortable Totally. But once you embrace muscle failure as the goal of the workout, it can become almost pleasure. The goal is not to burn calories while you’re exercising but to make your body burn them all the time. Running a few miles may make you sweat, but it expends only 100 calories per mile, and it doesn’t stimulate much bone or muscle development. Strength training doesn’t burn many calories, either. But when you push a muscle to failure, you set off a pour of physiological changes. As the muscle recovers over several days, it will thicken — and the new muscle tissue will demand sustenance. By the time you add three pounds of muscle, your body requires an extra 9, 000 calories a month just to break even. Hold your diet steady and, very quickly, you are vaporizing body fat. One might have benefited from any strength-training program. But advocates insist the slow technique is safer and more effective than traditional methods.In practicing slow lifting, one has to______.

A．complete each rep with great effort
B．try his best to do the training
C．suffer the bitter effect called forth by the exercise
D．exert extraordinary pressure on his legs and shoulders

单项选择题

Here’s a familiar version of the boy-meets-girl situation. A young man has at last plucked up courage to invite a dazzling young lady out to dinner. She has accepted his invitation and he is overjoyed. He is determined to take her to the best restaurant in town, even if it means that he will have to live on memories and hopes during the month to come. When they get to the restaurant, he discovers that this ethereal creature is on a diet. She mustn’t eat this and she mustn’t eat that. Oh, but of course, she doesn’t want to spoil his enjoyment. Let him by all means eat as much fattening food as he wants: it’s the surest way to an early grave. They spend a truly memorable evening together and never see each other again. What a miserable lot dieters are! You can always recognize them from the sour expression on their faces. They spend most of their time turning their noses up at food. They are forever consulting calorie charts; gazing at themselves in mirrors; and leaping on to weighing-machines in the bathroom. They spend a lifetime fighting a losing battle against spreading hips, protruding tummies and double chins. Some wage all-out war on FAT. Mere dieting is not enough. They exhaust themselves doing exercises, sweating in sauna baths, being pummeled and massaged by weird machines. The really wealthy diet-mongers pay vast sums for "health cures". For two weeks they can enter a nature clinic and be starved to death for a hundred guineas a week. Don’t think it’s only the middle-aged who go in for these fads either. Many of these bright young things you see are suffering from chronic malnutrition: they are living on nothing but air, water and the goodwill of God. Dieters undertake to starve themselves of their own free will; so why are they so miserable Well, for one thing, they’re always hungry. You can’t be hungry and happy at the same time. All the horrible concoctions they eat instead of food leave them permanently dissatisfied. Wonderfood is a complete food, the advertisement says. Just dissolve a teaspoonful in water. A complete food it may be, but not quite as complete as a juicy steak. And, of course, they’re always miserable because they feel so guilty. Hunger just proves too much for them and in the end they lash out and devour five huge guilt-inducing cream cakes at a sitting. And who can blame them At least three times a day they are exposed to temptation. What utter torture it is always watching others tucking into piles of mouth-watering food while you munch a water biscuit and sip unsweetened lemon juice! What’s all this self-inflicted torture for Saintly people deprive themselves of food to attain a state of grace. Unsaintly people do so to attain a state of misery. It will be a great day when all the dieters in the world abandon their slimming courses; when they hold out their plates and demand second helpings!Which of the following ways is NOT mentioned for diet

A．Doing exercises.
B．Not eating sugar.
C．Not eating fat.
D．Taking sauna baths.

单项选择题

Can electricity cause cancer In a society that literally runs on electric power, the very idea seems preposterous. But for more than a decade, a growing band of scientists and journalists has pointed to studies that seem to link exposure to electromagnetic fields with increased risk of leukemia and other malignancies. The implications are unsettling, to say the least, since everyone comes into contact with such fields, which are generated by everything electrical, from power lines and antennas to personal computers and micro-wave ovens. Because evidence on the subject is inconclusive and often contradictory, it has been hard to decide whether concern about the health effects of electricity is legitimate—or the worst kind of paranoia. Now the alarmists have gained some qualified support from the U. S. Environmental Protection Agency. In the executive summary of a new scientific review, released in draft form late last week, the EPA has put forward what amounts to the most serious government warning to date. The agency tentatively concludes that scientific evidence "suggests a casual link" between extremely low-frequency electromagnetic fields — those having very longwave-lengths — and leukemia, lymphoma and brain cancer, While the report falls short of classifying ELF fields as probable carcinogens, it does identify the common 60-hertz magnetic field as "a possible, but not proven, cause of cancer in humans". The report is no reason to panic—or even to lost sleep. If there is a cancer risk, it is a small one. The evidence is still so controversial that the draft stirred a great deal of debate within the Bush Administration, and the EPA released it over strong objections from the Pentagon and the White House. But now no one can deny that the issue must be taken seriously and that much more research is needed. At the heart of the debate is a simple and well-understood physical phenomenon: When an electric current passes through a wire, it generates an electromagnetic field that exerts forces on surrounding objects. For many years, scientists dismissed any suggestion that such forces might be harmful, primarily because they are so extraordinarily weak. The ELF magnetic field generated by a video terminal measures only a few milligauss, or about one-hundredth the strength of the earth’s own magnetic field. The electric fields surrounding a power line can be as high as 10 kilovolts per meter, but the corresponding field induced in human cells will be only about 1 millivolt per meter. This is far less than the electric fields that the cells themselves generate. How could such minuscule forces pose a health danger The consensus used to be that they could not, and for decades scientists concentrated on more powerful kinds of radiation, like X-rays, that pack sufficient wallop to knock electrons out of the molecules that make up the human body. Such "ionizing" radiations have been clearly linked to increased cancer risks and there are regulations to control emissions. But epidemiological studies, which find statistical associations between sets of data, do not prove cause and effect. Though there is a body of laboratory work showing that exposure to ELF fields can have biological effects on animal tissues, a mechanism by which those effects could lead to cancerous growths has never been found. The Pentagon is far from persuaded. In a blistering 33-page critique of the EPA report, Air Force scientists charge its authors with having "biased the entire document" toward proving a link. "Our reviewers are convinced that there is no suggestion that electromagnetic fields present in the environment induce or promote cancer, " the Air Force concludes. "It is astonishing that the EPA would lend its imprimatur on this report. " Then Pentagon’s concern is understandable. There is hardly a unit of the modern military that does not depend on the heavy use of some kind of electronic equipment, from huge ground-based radar towers to the defense systems built into every warship and plane.What do you think ordinary citizens may do after reading the different arguments

A．They are indifferent.
B．They are worried very much.
C．The may exercise prudent avoidance.
D．They are shocked.

单项选择题

For three decades we’ve heard endlessly about the virtues of aerobic (increasing oxygen consumption) exercise. Medical authorities have praised running and jumping as the key to good health, and millions of Americans have taken to the treadmill to reap the rewards. But the story is changing. Everyone from the American Heart Association to the surgeon general’s office has recently embraced strength training as a complement to aerobics. And as weight lifting has gone mainstream, so has the once obscure practice known as "Super Slow" training. Enthusiasts claim that by pumping iron at a snail’s pace — making each "rep" (repeat) last 14 seconds instead of the usual 7 — you can safely place extraordinary demands on your muscles, and call forth an extraordinary response. Slow lifting may not be the only exercise you need, as some advocates believe, but the benefits are often dramatic. Almost anyone can handle this routine. The only requirements are complete focus and a tolerance for deep muscular burn. For each exercise — leg press, bench press, shoulder press and so on — you set the machine to provide only moderate resistance. But as you draw out each repeat, depriving yourself of impetus, the weight soon feels unbearable. Defying the impulse to stop, you kept going until you can’t complete a repeat. Then you sustain your vain effort for 10 more seconds while the weight sinks gradually toward its cradle. Intense Uncomfortable Totally. But once you embrace muscle failure as the goal of the workout, it can become almost pleasure. The goal is not to burn calories while you’re exercising but to make your body burn them all the time. Running a few miles may make you sweat, but it expends only 100 calories per mile, and it doesn’t stimulate much bone or muscle development. Strength training doesn’t burn many calories, either. But when you push a muscle to failure, you set off a pour of physiological changes. As the muscle recovers over several days, it will thicken — and the new muscle tissue will demand sustenance. By the time you add three pounds of muscle, your body requires an extra 9, 000 calories a month just to break even. Hold your diet steady and, very quickly, you are vaporizing body fat. One might have benefited from any strength-training program. But advocates insist the slow technique is safer and more effective than traditional methods.While making each rep, one may suffer from______.

A．impetus loss
B．weight loss
C．bearable iron weights
D．the feeling of successful workout

单项选择题

Here’s a familiar version of the boy-meets-girl situation. A young man has at last plucked up courage to invite a dazzling young lady out to dinner. She has accepted his invitation and he is overjoyed. He is determined to take her to the best restaurant in town, even if it means that he will have to live on memories and hopes during the month to come. When they get to the restaurant, he discovers that this ethereal creature is on a diet. She mustn’t eat this and she mustn’t eat that. Oh, but of course, she doesn’t want to spoil his enjoyment. Let him by all means eat as much fattening food as he wants: it’s the surest way to an early grave. They spend a truly memorable evening together and never see each other again. What a miserable lot dieters are! You can always recognize them from the sour expression on their faces. They spend most of their time turning their noses up at food. They are forever consulting calorie charts; gazing at themselves in mirrors; and leaping on to weighing-machines in the bathroom. They spend a lifetime fighting a losing battle against spreading hips, protruding tummies and double chins. Some wage all-out war on FAT. Mere dieting is not enough. They exhaust themselves doing exercises, sweating in sauna baths, being pummeled and massaged by weird machines. The really wealthy diet-mongers pay vast sums for "health cures". For two weeks they can enter a nature clinic and be starved to death for a hundred guineas a week. Don’t think it’s only the middle-aged who go in for these fads either. Many of these bright young things you see are suffering from chronic malnutrition: they are living on nothing but air, water and the goodwill of God. Dieters undertake to starve themselves of their own free will; so why are they so miserable Well, for one thing, they’re always hungry. You can’t be hungry and happy at the same time. All the horrible concoctions they eat instead of food leave them permanently dissatisfied. Wonderfood is a complete food, the advertisement says. Just dissolve a teaspoonful in water. A complete food it may be, but not quite as complete as a juicy steak. And, of course, they’re always miserable because they feel so guilty. Hunger just proves too much for them and in the end they lash out and devour five huge guilt-inducing cream cakes at a sitting. And who can blame them At least three times a day they are exposed to temptation. What utter torture it is always watching others tucking into piles of mouth-watering food while you munch a water biscuit and sip unsweetened lemon juice! What’s all this self-inflicted torture for Saintly people deprive themselves of food to attain a state of grace. Unsaintly people do so to attain a state of misery. It will be a great day when all the dieters in the world abandon their slimming courses; when they hold out their plates and demand second helpings!What is the author’s attitude toward diet

A．Persuasive.
B．Critical.
C．Indifferent.
D．Adversative.

单项选择题

For three decades we’ve heard endlessly about the virtues of aerobic (increasing oxygen consumption) exercise. Medical authorities have praised running and jumping as the key to good health, and millions of Americans have taken to the treadmill to reap the rewards. But the story is changing. Everyone from the American Heart Association to the surgeon general’s office has recently embraced strength training as a complement to aerobics. And as weight lifting has gone mainstream, so has the once obscure practice known as "Super Slow" training. Enthusiasts claim that by pumping iron at a snail’s pace — making each "rep" (repeat) last 14 seconds instead of the usual 7 — you can safely place extraordinary demands on your muscles, and call forth an extraordinary response. Slow lifting may not be the only exercise you need, as some advocates believe, but the benefits are often dramatic. Almost anyone can handle this routine. The only requirements are complete focus and a tolerance for deep muscular burn. For each exercise — leg press, bench press, shoulder press and so on — you set the machine to provide only moderate resistance. But as you draw out each repeat, depriving yourself of impetus, the weight soon feels unbearable. Defying the impulse to stop, you kept going until you can’t complete a repeat. Then you sustain your vain effort for 10 more seconds while the weight sinks gradually toward its cradle. Intense Uncomfortable Totally. But once you embrace muscle failure as the goal of the workout, it can become almost pleasure. The goal is not to burn calories while you’re exercising but to make your body burn them all the time. Running a few miles may make you sweat, but it expends only 100 calories per mile, and it doesn’t stimulate much bone or muscle development. Strength training doesn’t burn many calories, either. But when you push a muscle to failure, you set off a pour of physiological changes. As the muscle recovers over several days, it will thicken — and the new muscle tissue will demand sustenance. By the time you add three pounds of muscle, your body requires an extra 9, 000 calories a month just to break even. Hold your diet steady and, very quickly, you are vaporizing body fat. One might have benefited from any strength-training program. But advocates insist the slow technique is safer and more effective than traditional methods.The phrase "to break even"(Para. 3)most likely means______.

A．to upset the physical energy balance
B．to disturb the calmness of the body
C．to gain a greater profit than a loss
D．to make neither a profit nor a loss

单项选择题

Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide. All birds are thought to be susceptible to infection with avian influenza, though some species are more resistant to infection than others. Infection causes a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is known as "highly pathogenic avian influenza". This form is characterized by sudden onset, severe illness, and rapid death, with a mortality that can approach 100%. Fifteen subtypes of influenza virus are known to infect birds, thus providing an extensive reservoir of influenza viruses potentially circulating in bird populations. To date, all outbreaks of the highly pathogenic form have been caused by influenza A viruses of subtypes H5 and H7. Migratory waterfowl — most notably wild ducks — are the natural reservoir of avian influenza viruses, and these birds are also the most resistant to infection. Domestic poultry, including chickens and turkeys, are particularly susceptible to epidemics of rapidly fatal influenza. Direct or indirect contact of domestic flocks with wild migratory waterfowl has been implicated as a frequent cause of epidemics. Live bird markets have also played an important role in the spread of epidemics. Recent research has shown that viruses of low pathogenicity can, after circulation for sometimes short periods in a poultry population, mutate into highly pathogenic viruses. During a 1983-1984 epidemic in the United States of America, the H5N2 virus initially caused low mortality, but within six months became highly pathogenic, with a mortality approaching 90%. Control of the outbreak required destruction of more than 17 million birds at a cost of nearly US$ 65 million. During a 1999-2001 epidemic in Italy, the H7N1 virus, initially of low pathogenicity, mutated within 9 months to a highly pathogenic form. More than 13 million birds died or were destroyed. The quarantining of infected farms and destruction of infected or potentially exposed flocks are standard control measures aimed at preventing spread to other farms and eventual establishment of the virus in a country’s poultry population. Apart from being highly contagious, avian influenza viruses are readily transmitted from farm to farm by mechanical means, such as by contaminated equipment, vehicles, feed, cages, or clothing. Highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low. Stringent sanitary measures on farms can, however, confer some degree of protection. In the absence of prompt control measures backed by good surveillance, epidemics can last for years. For example, an epidemic of H5N2 avian influenza, which began in Mexico in 1992, started with low pathogenicity, evolved to the highly fatal form, and was not controlled until 1995.According to the passage, the following are all incorrect EXCEPT______.

A．avian influenza was not recognized until more than 100 years ago
B．infection with avian influenza cause mild epidemics in birds
C．not all birds are susceptible to infection with avian influenza
D．the disease of avian influenza occurs worldwide except in Italy

单项选择题

Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide. All birds are thought to be susceptible to infection with avian influenza, though some species are more resistant to infection than others. Infection causes a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is known as "highly pathogenic avian influenza". This form is characterized by sudden onset, severe illness, and rapid death, with a mortality that can approach 100%. Fifteen subtypes of influenza virus are known to infect birds, thus providing an extensive reservoir of influenza viruses potentially circulating in bird populations. To date, all outbreaks of the highly pathogenic form have been caused by influenza A viruses of subtypes H5 and H7. Migratory waterfowl — most notably wild ducks — are the natural reservoir of avian influenza viruses, and these birds are also the most resistant to infection. Domestic poultry, including chickens and turkeys, are particularly susceptible to epidemics of rapidly fatal influenza. Direct or indirect contact of domestic flocks with wild migratory waterfowl has been implicated as a frequent cause of epidemics. Live bird markets have also played an important role in the spread of epidemics. Recent research has shown that viruses of low pathogenicity can, after circulation for sometimes short periods in a poultry population, mutate into highly pathogenic viruses. During a 1983-1984 epidemic in the United States of America, the H5N2 virus initially caused low mortality, but within six months became highly pathogenic, with a mortality approaching 90%. Control of the outbreak required destruction of more than 17 million birds at a cost of nearly US$ 65 million. During a 1999-2001 epidemic in Italy, the H7N1 virus, initially of low pathogenicity, mutated within 9 months to a highly pathogenic form. More than 13 million birds died or were destroyed. The quarantining of infected farms and destruction of infected or potentially exposed flocks are standard control measures aimed at preventing spread to other farms and eventual establishment of the virus in a country’s poultry population. Apart from being highly contagious, avian influenza viruses are readily transmitted from farm to farm by mechanical means, such as by contaminated equipment, vehicles, feed, cages, or clothing. Highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low. Stringent sanitary measures on farms can, however, confer some degree of protection. In the absence of prompt control measures backed by good surveillance, epidemics can last for years. For example, an epidemic of H5N2 avian influenza, which began in Mexico in 1992, started with low pathogenicity, evolved to the highly fatal form, and was not controlled until 1995.Characters of the highly pathogenic avian influenza include EXCEPT______.

A．sudden onset
B．resistance to infection
C．severe illness
D．rapid death

单项选择题

Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide. All birds are thought to be susceptible to infection with avian influenza, though some species are more resistant to infection than others. Infection causes a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is known as "highly pathogenic avian influenza". This form is characterized by sudden onset, severe illness, and rapid death, with a mortality that can approach 100%. Fifteen subtypes of influenza virus are known to infect birds, thus providing an extensive reservoir of influenza viruses potentially circulating in bird populations. To date, all outbreaks of the highly pathogenic form have been caused by influenza A viruses of subtypes H5 and H7. Migratory waterfowl — most notably wild ducks — are the natural reservoir of avian influenza viruses, and these birds are also the most resistant to infection. Domestic poultry, including chickens and turkeys, are particularly susceptible to epidemics of rapidly fatal influenza. Direct or indirect contact of domestic flocks with wild migratory waterfowl has been implicated as a frequent cause of epidemics. Live bird markets have also played an important role in the spread of epidemics. Recent research has shown that viruses of low pathogenicity can, after circulation for sometimes short periods in a poultry population, mutate into highly pathogenic viruses. During a 1983-1984 epidemic in the United States of America, the H5N2 virus initially caused low mortality, but within six months became highly pathogenic, with a mortality approaching 90%. Control of the outbreak required destruction of more than 17 million birds at a cost of nearly US$ 65 million. During a 1999-2001 epidemic in Italy, the H7N1 virus, initially of low pathogenicity, mutated within 9 months to a highly pathogenic form. More than 13 million birds died or were destroyed. The quarantining of infected farms and destruction of infected or potentially exposed flocks are standard control measures aimed at preventing spread to other farms and eventual establishment of the virus in a country’s poultry population. Apart from being highly contagious, avian influenza viruses are readily transmitted from farm to farm by mechanical means, such as by contaminated equipment, vehicles, feed, cages, or clothing. Highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low. Stringent sanitary measures on farms can, however, confer some degree of protection. In the absence of prompt control measures backed by good surveillance, epidemics can last for years. For example, an epidemic of H5N2 avian influenza, which began in Mexico in 1992, started with low pathogenicity, evolved to the highly fatal form, and was not controlled until 1995.Migratory waterfowl are the most resistant to the infection with avian influenza______.

A．when they would migrate to the south from the north
B．if they do not migrate to the rest of the planet
C．when they are mixed with domestic poultry and pigs
D．while domestic poultry are particularly susceptible to epidemics of avian influenza

单项选择题

About ten men in every hundred suffer from color blindness in some way; women are luckier only about one in two hundred is affected in this manner. There are different forms of color blindness. A man may not be able to see deep red. He may think that red, orange and yellow are all shades of green. Sometimes a person cannot tell the difference between blue and green. In rare cases an unlucky man may see everything in shades of green—a strange world indeed. In certain occupations color blindness can be dangerous and candidates are tested most carefully. For example, when fighting at night, soldiers use lights of flares to signal to each other. A green light may mean "Advance" and a red light may mean: "Danger! Keep back!" You can see what will happen if somebody thinks that red is green! Color blindness in human beings is a strange thing to explain. In a single eye there are millions of very small things called "cones". These help to see in a bright light and to tell the difference between colors. There are also millions of "rods" but these are used for seeing when it is nearly dark. They show us shape but not color. Wait until it is dark tonight, then go outside. Look round you and try to see what colors you can recognize. Birds and animals which hunt at night have eyes which contain few or no cones at all, so they cannot see colors. As far as we know, bats and adult owls cannot see colors at all only light and dark shapes. Similarly cats and dogs cannot see colours as well as we can. Insects can see ultra violet rays which are invisible to us, and some of them can even see X rays. The wings of a moth may seem grey and dull to us, but to insects they may appear beautiful, showing colors which we cannot see. Scientists know that there are other colors around us which insects can see but which we cannot see. Some insects have favorite colors. Mosquitoes like blue, but do not like yellow. A red light will not attract insects but a blue lamp will.Among people who suffer from color blindness, ______.

A．some may see everything in shades of green
B．few can tell the difference between blue and green
C．few may think that red, orange and yellow are all shades of green
D．very few may think that everything in the world is in green

单项选择题

Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide. All birds are thought to be susceptible to infection with avian influenza, though some species are more resistant to infection than others. Infection causes a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is known as "highly pathogenic avian influenza". This form is characterized by sudden onset, severe illness, and rapid death, with a mortality that can approach 100%. Fifteen subtypes of influenza virus are known to infect birds, thus providing an extensive reservoir of influenza viruses potentially circulating in bird populations. To date, all outbreaks of the highly pathogenic form have been caused by influenza A viruses of subtypes H5 and H7. Migratory waterfowl — most notably wild ducks — are the natural reservoir of avian influenza viruses, and these birds are also the most resistant to infection. Domestic poultry, including chickens and turkeys, are particularly susceptible to epidemics of rapidly fatal influenza. Direct or indirect contact of domestic flocks with wild migratory waterfowl has been implicated as a frequent cause of epidemics. Live bird markets have also played an important role in the spread of epidemics. Recent research has shown that viruses of low pathogenicity can, after circulation for sometimes short periods in a poultry population, mutate into highly pathogenic viruses. During a 1983-1984 epidemic in the United States of America, the H5N2 virus initially caused low mortality, but within six months became highly pathogenic, with a mortality approaching 90%. Control of the outbreak required destruction of more than 17 million birds at a cost of nearly US$ 65 million. During a 1999-2001 epidemic in Italy, the H7N1 virus, initially of low pathogenicity, mutated within 9 months to a highly pathogenic form. More than 13 million birds died or were destroyed. The quarantining of infected farms and destruction of infected or potentially exposed flocks are standard control measures aimed at preventing spread to other farms and eventual establishment of the virus in a country’s poultry population. Apart from being highly contagious, avian influenza viruses are readily transmitted from farm to farm by mechanical means, such as by contaminated equipment, vehicles, feed, cages, or clothing. Highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low. Stringent sanitary measures on farms can, however, confer some degree of protection. In the absence of prompt control measures backed by good surveillance, epidemics can last for years. For example, an epidemic of H5N2 avian influenza, which began in Mexico in 1992, started with low pathogenicity, evolved to the highly fatal form, and was not controlled until 1995.Control of the outbreak requires EXCEPT______.

A．destruction of infected or potentially exposed flocks
B．the quarantining of infected farms
C．the absence of prompt control measures
D．stringent sanitary measures on farms

单项选择题

About ten men in every hundred suffer from color blindness in some way; women are luckier only about one in two hundred is affected in this manner. There are different forms of color blindness. A man may not be able to see deep red. He may think that red, orange and yellow are all shades of green. Sometimes a person cannot tell the difference between blue and green. In rare cases an unlucky man may see everything in shades of green—a strange world indeed. In certain occupations color blindness can be dangerous and candidates are tested most carefully. For example, when fighting at night, soldiers use lights of flares to signal to each other. A green light may mean "Advance" and a red light may mean: "Danger! Keep back!" You can see what will happen if somebody thinks that red is green! Color blindness in human beings is a strange thing to explain. In a single eye there are millions of very small things called "cones". These help to see in a bright light and to tell the difference between colors. There are also millions of "rods" but these are used for seeing when it is nearly dark. They show us shape but not color. Wait until it is dark tonight, then go outside. Look round you and try to see what colors you can recognize. Birds and animals which hunt at night have eyes which contain few or no cones at all, so they cannot see colors. As far as we know, bats and adult owls cannot see colors at all only light and dark shapes. Similarly cats and dogs cannot see colours as well as we can. Insects can see ultra violet rays which are invisible to us, and some of them can even see X rays. The wings of a moth may seem grey and dull to us, but to insects they may appear beautiful, showing colors which we cannot see. Scientists know that there are other colors around us which insects can see but which we cannot see. Some insects have favorite colors. Mosquitoes like blue, but do not like yellow. A red light will not attract insects but a blue lamp will.When millions of rods in our eyes are at work in darkness we can see______.

A．colors only
B．shapes and colors
C．shapes only
D．darkness only

单项选择题

Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide. All birds are thought to be susceptible to infection with avian influenza, though some species are more resistant to infection than others. Infection causes a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is known as "highly pathogenic avian influenza". This form is characterized by sudden onset, severe illness, and rapid death, with a mortality that can approach 100%. Fifteen subtypes of influenza virus are known to infect birds, thus providing an extensive reservoir of influenza viruses potentially circulating in bird populations. To date, all outbreaks of the highly pathogenic form have been caused by influenza A viruses of subtypes H5 and H7. Migratory waterfowl — most notably wild ducks — are the natural reservoir of avian influenza viruses, and these birds are also the most resistant to infection. Domestic poultry, including chickens and turkeys, are particularly susceptible to epidemics of rapidly fatal influenza. Direct or indirect contact of domestic flocks with wild migratory waterfowl has been implicated as a frequent cause of epidemics. Live bird markets have also played an important role in the spread of epidemics. Recent research has shown that viruses of low pathogenicity can, after circulation for sometimes short periods in a poultry population, mutate into highly pathogenic viruses. During a 1983-1984 epidemic in the United States of America, the H5N2 virus initially caused low mortality, but within six months became highly pathogenic, with a mortality approaching 90%. Control of the outbreak required destruction of more than 17 million birds at a cost of nearly US$ 65 million. During a 1999-2001 epidemic in Italy, the H7N1 virus, initially of low pathogenicity, mutated within 9 months to a highly pathogenic form. More than 13 million birds died or were destroyed. The quarantining of infected farms and destruction of infected or potentially exposed flocks are standard control measures aimed at preventing spread to other farms and eventual establishment of the virus in a country’s poultry population. Apart from being highly contagious, avian influenza viruses are readily transmitted from farm to farm by mechanical means, such as by contaminated equipment, vehicles, feed, cages, or clothing. Highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low. Stringent sanitary measures on farms can, however, confer some degree of protection. In the absence of prompt control measures backed by good surveillance, epidemics can last for years. For example, an epidemic of H5N2 avian influenza, which began in Mexico in 1992, started with low pathogenicity, evolved to the highly fatal form, and was not controlled until 1995.From the passage we can infer that rapid mutation of low to highly pathogenic viruses______.

A．has led to evolution of the highly fatal form H5N2 viruses
B．makes it impossible for scientists to develop more effective vaccines against the viruses
C．helps to prevent spread from farm to farm by mechanical means
D．proves to be protective of the extensive reservoirs

单项选择题

About ten men in every hundred suffer from color blindness in some way; women are luckier only about one in two hundred is affected in this manner. There are different forms of color blindness. A man may not be able to see deep red. He may think that red, orange and yellow are all shades of green. Sometimes a person cannot tell the difference between blue and green. In rare cases an unlucky man may see everything in shades of green—a strange world indeed. In certain occupations color blindness can be dangerous and candidates are tested most carefully. For example, when fighting at night, soldiers use lights of flares to signal to each other. A green light may mean "Advance" and a red light may mean: "Danger! Keep back!" You can see what will happen if somebody thinks that red is green! Color blindness in human beings is a strange thing to explain. In a single eye there are millions of very small things called "cones". These help to see in a bright light and to tell the difference between colors. There are also millions of "rods" but these are used for seeing when it is nearly dark. They show us shape but not color. Wait until it is dark tonight, then go outside. Look round you and try to see what colors you can recognize. Birds and animals which hunt at night have eyes which contain few or no cones at all, so they cannot see colors. As far as we know, bats and adult owls cannot see colors at all only light and dark shapes. Similarly cats and dogs cannot see colours as well as we can. Insects can see ultra violet rays which are invisible to us, and some of them can even see X rays. The wings of a moth may seem grey and dull to us, but to insects they may appear beautiful, showing colors which we cannot see. Scientists know that there are other colors around us which insects can see but which we cannot see. Some insects have favorite colors. Mosquitoes like blue, but do not like yellow. A red light will not attract insects but a blue lamp will.According to the passage, bats and adult owls cannot see colors______.

A．because they hunt at night
B．because they cannot see light
C．because they have no cones and rods
D．because they have no cones

单项选择题

About ten men in every hundred suffer from color blindness in some way; women are luckier only about one in two hundred is affected in this manner. There are different forms of color blindness. A man may not be able to see deep red. He may think that red, orange and yellow are all shades of green. Sometimes a person cannot tell the difference between blue and green. In rare cases an unlucky man may see everything in shades of green—a strange world indeed. In certain occupations color blindness can be dangerous and candidates are tested most carefully. For example, when fighting at night, soldiers use lights of flares to signal to each other. A green light may mean "Advance" and a red light may mean: "Danger! Keep back!" You can see what will happen if somebody thinks that red is green! Color blindness in human beings is a strange thing to explain. In a single eye there are millions of very small things called "cones". These help to see in a bright light and to tell the difference between colors. There are also millions of "rods" but these are used for seeing when it is nearly dark. They show us shape but not color. Wait until it is dark tonight, then go outside. Look round you and try to see what colors you can recognize. Birds and animals which hunt at night have eyes which contain few or no cones at all, so they cannot see colors. As far as we know, bats and adult owls cannot see colors at all only light and dark shapes. Similarly cats and dogs cannot see colours as well as we can. Insects can see ultra violet rays which are invisible to us, and some of them can even see X rays. The wings of a moth may seem grey and dull to us, but to insects they may appear beautiful, showing colors which we cannot see. Scientists know that there are other colors around us which insects can see but which we cannot see. Some insects have favorite colors. Mosquitoes like blue, but do not like yellow. A red light will not attract insects but a blue lamp will.According to the passage, dogs and cats______.

A．as well as human beings can not see some colors
B．have fewer cones than human beings
C．have less rods than human beings
D．can see colors as well as human beings

单项选择题

About ten men in every hundred suffer from color blindness in some way; women are luckier only about one in two hundred is affected in this manner. There are different forms of color blindness. A man may not be able to see deep red. He may think that red, orange and yellow are all shades of green. Sometimes a person cannot tell the difference between blue and green. In rare cases an unlucky man may see everything in shades of green—a strange world indeed. In certain occupations color blindness can be dangerous and candidates are tested most carefully. For example, when fighting at night, soldiers use lights of flares to signal to each other. A green light may mean "Advance" and a red light may mean: "Danger! Keep back!" You can see what will happen if somebody thinks that red is green! Color blindness in human beings is a strange thing to explain. In a single eye there are millions of very small things called "cones". These help to see in a bright light and to tell the difference between colors. There are also millions of "rods" but these are used for seeing when it is nearly dark. They show us shape but not color. Wait until it is dark tonight, then go outside. Look round you and try to see what colors you can recognize. Birds and animals which hunt at night have eyes which contain few or no cones at all, so they cannot see colors. As far as we know, bats and adult owls cannot see colors at all only light and dark shapes. Similarly cats and dogs cannot see colours as well as we can. Insects can see ultra violet rays which are invisible to us, and some of them can even see X rays. The wings of a moth may seem grey and dull to us, but to insects they may appear beautiful, showing colors which we cannot see. Scientists know that there are other colors around us which insects can see but which we cannot see. Some insects have favorite colors. Mosquitoes like blue, but do not like yellow. A red light will not attract insects but a blue lamp will.Which of the following is NOT true about insects

A．Insects can see more colors than human beings.
B．Insects can see ultraviolet rays which are invisible to men.
C．All insects have their favorite colors.
D．The world is more colorful to insects than to human beings.

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