题目内容：

缺词填空

Trees are u    1.  to men in three important ways. They p  2.  them with wood and other things. They give people shade in hot days ,and they help to prevent drought(干旱) and floods（洪水）.

S  3.  , in many places of the world, men don’t know the third of these is the most important. They just want to make  money  from the trees. Some people cut down a large    n   4.   of trees in the forests. Usually they are too busy c  5. down trees to plant and look after new  trees so the forests  slowly b  6.   smaller and smaller.

This does not only m  7. that men will have fewer trees. The r  8.  are even more serious. For where there are trees, their roots can prevent  the rain from w  9.   away the soil, but if there are no trees, the rain falls on hard ground and wash away the rich top-soil (地表土). When the top-soil is gone, n  10.    remains but death.