Trees are useful to men in three important ways:They p 1 them with wood andTrees are useful to men in three important ways:They p 1 them with wood and other products,they give them shade,and they help to p 2 drought and floods.Unfortunately（不幸

Trees are useful to men in three important ways:They p 1 them with wood andTrees are useful to men in three important ways:They p 1 them with wood and other products,they give them shade,and they help to p 2 drought and floods.Unfortunately（不幸
Trees are useful to men in three important ways:They p 1 them with wood and
Trees are useful to men in three important ways:They p 1 them with wood and other products,they give them shade,and they help to p 2 drought and floods.Unfortunately（不幸运地）,in many p 3 of the world,men don’t know that the third of these is the most important.In their eagerness（渴望） of making m 4 from trees,some people cut trees down in large n 5 reserves.And besides,they are usually too c 6 to plant and look after new trees,so the forests slowly b 7 smaller and smaller.This does not only mean that men will have fewer trees.The results are e 8 more serious:For where there are trees,their roots(根) prevent the rain from washing away the soil,but there are no trees,the rain falls on hard g 9 and flows away,causing f 10 and carrying away the rich top-soil（地表土）.When all the top-soil is gone,nothing remains（剩下） but death.

Trees are useful to men in three important ways:They p 1 them with wood andTrees are useful to men in three important ways:They p 1 them with wood and other products,they give them shade,and they help to p 2 drought and floods.Unfortunately（不幸
Trees are useful to men in three important ways:They【1.provide】 them with wood and other products,they give them shade,and they help to【2.prevent】drought and floods.
Unfortunately ,in many【3.parts】of the world,men don’t know that the third of these is the most important.In their eagerness of making【4.money】from trees,some people cut trees down in large【5.natural】 reserves.And besides,they are usually too【6.careless】to plant and look after new trees,so the forests slowly【7.become】smaller and smaller.This does not only mean that men will have fewer trees.The results are【8.even】more serious:For where there are trees,their roots prevent the rain from washing away the soil,but there are no trees,the rain falls on hard【9.ground】and flows away,causing【10.floods】and carrying away the rich top-soil.When all the top-soil is gone,nothing remains but death.

1provide2prevent3parts4more5 6cruel7become8even9 10flood 不好意思，有两空暂时没有想出来。