Trees are useful to man in three important ways: they provide him with wood a

游客2024-07-06  11

问题    Trees are useful to man in three important ways: they provide him with wood and other products; they give him shade; and they help to prevent droughts and floods.
   Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important one. In eagerness to make money from trees, men have cut them down in large numbers. And besides, men are usually too careless to plant and look after new trees. So the forests slowly disappear.
   This does not only mean that man will have fewer trees. The results are even more serious: for where there are trees, their roots break up soil--allowing the rain to sink in--and also bind the soil, thus preventing it from being washed away easily; but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When all the top-soil is gone, nothing remains but worthless desert.
   Two thousand years ago a rich and powerful country cut down its trees to build war- ships, with which to gain itself an empire. It set up the empire but, without its trees, its soil became poor and it grew weak. When the empire fell to pieces, the home country found itself faced with floods and starvation.

选项 A、They help him make money.
B、They give him wood and other products.
C、They help him prevent droughts and floods.
D、They give him shade.

答案 C

解析 细节题。从文章的第一段和第二段第一句话可知:树木的三个功能中人们没有意识到的是阻止旱灾和水灾的发生。
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