Trees are useful to man in three important ways: they provide him with wood and other products: they give him shade:and they hel

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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. In his eagerness to make money from trees, he has cut them down inlarge numbers, only to find that without them he has lost the best friends he had. And besides, he is 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 ran falls on hard ground and flows away, causing floods and canying 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 warships, 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.
What does the author tell us in this passage?

选项 A、How trees help prevent droughts and floods
B、The relationship between trees and man
C、How an empire fell to pieces in ancient times
D、A story of trees

答案A

解析 概括主旨题。文章主要是说树木对人类的作用,然后论述树木怎样影晌人类,也就是作者想要告诉人们树木可以帮助预防洪水和干旱。
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