第一节 完形填空(共10小题；每小题1.5分，满分15分)
Trees are useful to man in three very important ways. They provide him with wood and other __21__ ; they give him shade; they help to prevent drought(干旱)and __22__.
Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important.
Two thousand years ago a rich and powerful country cut down its trees to build warships, with which to gain itself an empire. It gained the empire, but,__23__its trees, its soil became hard and poor. When the empire fell to__24__,the home country found itself faced by floods and starvation.
Even where a government realizes the importance of a plentiful supply of trees, it is difficult for__25__to persuade the villager to see this. The villager wants wood to cook his food with ; and he can earn money by making charcoal or selling wood to the townsman. He is usually too lazy or too careless to plant and look after new trees. So, unless the government has a good system of control, or can__26__the people, the forests will slowly disappear.
This does not only mean that the villagers’ sons and grandsons have__27__trees. The results are even more serious; for where there are trees, their roots break the soil up—allowing the rain to sink in—and also bind(结合)the soil, thus preventing its__28__washed away easily, but where there are no trees ,the rain falls on hard ground and carrying__29__with it the rich top soil, in which crops__30__so well. With all the topsoil gone, nothing remains but worthless desert.
21．A. uses B. products C. production D. result
22．A. floods B. soil C. air D .sunlight
23．A. with B. by C. on D. without
24．A. break B. unite C. bits D. pieces
25．A. it B. them C. he D. they
26．A. ask B. educate C. want D. remove
27．A. a few B. fewer C. a little D. little
28．A. been B. being C. is D. was
29．A. away B. off C. with D. by
30．A. come B. grow C. get D. turn