Trees are useful to men in three important ways:they give th

Trees are useful to men in three important ways:they give them with wood and other products,they give them shade,and they help to prevent drought (干旱) and floods (水灾).Unfortunately,in many parts of the world,men have not known that the third of these left trees are the most important.In their eagerness (渴望) of making money from trees,some people have cut trees down in large numbers,only to find that without them they have lost the best friends they had.And besides,they are usually too careless to plant and look after new trees,so the forests slowly become smaller and smaller.This does not only mean that men will have fewer trees.The results are even more serious:for where there are trees,their roots(根)break up soil-allowing the rain to sink in-and also bind(固定)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 (地表土).When all the top-soil is gone,nothing remains(剩下)but desert.
（ ）1.The most important service of trees to men is ________.
A.they help them to make money B.they help them to prevent drought and floods C.they give them shade and cool D.they give them wood and other products
（ ）2.In many places forests slowly disappear because ________.
A.many trees have been cut down B.new trees are not well looked after C.men have not paid enough attention to planting trees D.All of the above
（ ）3.Land becomes desert after all trees are cut down because ________.
A.roots of trees break up the soil B.there is too much rain C.of strong winds D.there are no more trees to keep the rich top-soil from being carried away by floods
（ ）4.Some people cut down a large number of trees because ________.
A.they were eager to get wood from them B.they were eager to make money from them C.they didn't realize the importance of them D.Both B and C
（ ）5.Which of the following is not true?
A.Trees can prevent drought and floods.B.Tree roots can break up soil.C.Tree roots can make the top-soil rich and the ground hard.D.Trees can make the rain sink into ground.

1 B 2 D 3 D 4 D 5 B
应该错不了
第一题选B 理由（the third of these left trees are the most important 第三点最重要）
第三点就是they help them to prevent drought and floods