Trees
Trees are useful to man in three very important ways: they provide him with wood and other products; they give him shade; and they help(51)drought and floods.
Unfortunately, in many parts of the world, man has not(52)that the third of these services is the most important. In his eagerness (渴望) to draw quick profit from the trees, he has cut them down in large(53), only to find that with the trees used he has lost the best friends he had. Two thousand years ago a rich and powerful country cut down its(54)to build warships with which to gain itself an empire. It gained the empire but without its trees, its soil became hard and(55). When the empire fell to pieces, the home country found(56)faced with floods and starvation.
Even where a government realizes the.(57)of a rich supply of trees, it is difficult for it to persuade the villager to see this. The villager wants wood to(58)his food with; and he can earn money(59)making charcoal (木炭) or selling wood to the townsman. He is usually too lazy or(60)careless to plant and look after new trees. So, unless the government has a good(61)of control, or can educate the people, the forests will slowly disappear.
This does not only(62)that the villagers' sons and grandsons have fewer trees. The results are even more(63). For where there are trees, their roots break up the soil allowing the rain to sink in and also bind the soil, thus preventing the(64)from being washed away easily. But where there are no trees, the rain falls on hard ground and flows away on the surface, causing floods and carrying away with it the top-soil, in(65)crops grow so well. When all the top-soil is gone, nothing remains but worthless desert.
A．give
B．use
C．prevent
D．lead