Trees are useful in three important【小题1】.The most important way is that they provide man with food , wood and other products. Trees provide food not only for man, but also for animals.【小题2】trees, many animals could not live on the earth. It’s not【小题3】 for man to live on the earth, either. The second important way is that trees give us shade(树荫). On a hot summer day, people are eager to have a rest under the shade of a tree after【小题4】 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【小题5】 droughts and flood. However, in many parts of the world, man hasn’t realized it. He has cut trees down in large numbers. In the end, he finds that he has lost the best friends he had.