Trees are our friends on Earth. They are useful to us in three very important ways.
Trees provide food not only for man but also for many animals. Without trees, many animals could not live on Earth.
The second important way is that trees give us shade. On a hot summer day, people like to have a rest under the shade of a tree after they have walked a long way.
The third important way is that trees help prevent droughts and floods（旱灾和水灾）. They have cut trees down in large numbers.
A. The same thing will happen to men, too.
B. In the end they find that they have lost the best friends they ever had.
C. The first important way is that they provide man with food, wood and other products.
D. However, in many parts of the world, people have not realized it.
E. You can imagine how important it is to people.
