Trees are usefully to us in three important ways：

1．________

they give us wood and another products;

2．________

they give us shade and they help to stopping droughts and floods

3．________

However, people in many part of the world

4．________

have not realized that the third benefit

5．________

is the more important．A large number of

6．________

trees have cut down, but new ones

7．________

haven’t been planted．It is really danger

8．________

for people．Though we do not try to keep the balance of nature,

9．________

we will lose our live environment．

10．________