Trees are useful to man in three very important ways. The first important way is that they provide man with food，wood and other products. Trees provide man and animals with food to live on the earth. It’s not easy for man to live on the earth without trees.

The second important way is that trees give us shade. On a hot summer day，people are eager to（急于）have a rest under the shade of a tree after they have walked a long way. You can imagine how important the shade of a tree is to man and animals.

The third important way is that trees help to prevent droughts and floods. However，in many parts of the world，man has not realized the third important way. He has cut trees down in large numbers. In the end he finds that he has lost the best friends he once had.

小题1:Is it easy for man to live on the earth without trees?

小题2:What is the first important way that trees bring us?

小题3:Where are people eager to rest after they have walked a long way?

小题4:In the end he finds he has lost the best friends he once had. What does ‘the best friends” here mean?

小题5:What should we do in order to protect trees?

多面体的结构可分为（）和（）两大类。

A.垒积结构

B.网架结构

C.球体结构

D.棱柱体结构

E.多面体结构