第6部分：完形填空（第51～65题，每题1分，共15分）
阅读下面的短文，文中有15处空白，每处空白给出4个选项，请根据短文的内容从4个选项中选择l个最佳答案，涂在答题卡相应的位置上。
rees
Trees are useful to man in three very important ways: they provide him 51 wood and other products; they give him shade; and they help prevent 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 tress, he has cut them down in large 53 , only to find that with the trees used he has lost the best visitors he had. Tow 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 itself faced with floods and starvation.
Even when a government realizes the 56 of a rich supply of trees, it is difficult for it to persuade the 57 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 62 .
This does not only 63 that the villagers' sons and grandsons have fewer trees. The results are even more 64 : for where there are trees their roots break the soil up — following the rain to sink in — and also bind the soil, thus preventing the 65 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 which crops grow so well. When all the top-soil is gone, nothing remains but worthless desert.
51.A. with B. on C. at D. in
52.A. hoped B. realizedC. promised D. planned
53.A. sense B. things C. prices D. numbers
54.A. bricks B. hills C. trees D. crops
55.A. rich B. poor C. famous D. enough
56.A. practice B. importance C. feeling D. space
57.A. enemy B. hero C. son D. villager
58.A. eat B. sell C. grow D. cook
59.A. by B. to C. beside D. down
60.A. well B. towards C. too D. along
61.A. event B. system C. supply D. figure
62.A. disappear B. grow C. arise D. spread
63.A. mean B. believe C. talk D. understand
64.A. reliable B. useful C. serious D. limited
65.A. floods B. rocks C. villagers D. soil
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