单项选择题X 纠错
Throughout history man has had to accept the fact that all living things must die, but people now live longer than they (36) . Yet, all living things still show the (37) of aging, which will eventually. (38) death.
Aging is not a disease, but as a person passes maturity, the cells of the body and the (39) they form do not function as well as they (40) in childhood and adolescence (青春期). The body provides less (41) against disease and is more prone (42) accident.A number of related cause may (43) aging. Some cells of the body have a fairly long life, but they are not (44) when they die. As a person ages, (45) of brain cells and muscle cells decrease, (46) body cells die and are replaced by new cells. In an aging person the (47) cells may not be as viable (能生存的) or as capable (48) growth as those of a young person.Another (49) in aging may be changes within the cells (50) . Some of the protein chemicals in cells are known (51) with age and become less elastic. This is why the skin of old people wrinkles and (52) . This is also the reason old people (53) in height. There may be other more important chemical changes in the cells. Some complex cell chemicals, such as RNA, store and (54) information that the cell need. Aging may affect this (55) and change the information carrying molecules so that they do not transmit the information as well.
A. a number
B. the amount
C. the number
D. most
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单项选择题
Every year gray whales migrate from the Bering Sea in Alaska to the Baja Peninsula in Mexico.
Eleven gray whales have died in the San Francisco Bay in the last three weeks. No one knows why the whales are dying.
Last year 270 whales died along the whales’ migration route. Many people think starvation is the cause. This year the dead whales seem to have more blubber (fat) on them.
Twenty years ago, the gray whale was listed as an endangered species.
Some scientists think that the larger number of whales makes it hard to find enough food. More whales create more pressure on the food supply, a supply that some scientists say may have dwindled as a result of the warm waters of El Nino.
Most of the whales have been dead for many days before they are found and studied. This makes it hard to find the reason for death.
65 whales have been seen in the San Francisco Bay Area this year compared to 17 last year. The whales could be dying from many diseases, but it may be over-population.
A. Twice as many.
B. Three times as many.
C. Half as many.
D. About the same.
