Trees are useful to man in three ways. Firstly, they provide man with food, wood and other products. Without trees, animals could not live on the earth.
树对人的益处有三个方面。首先，它们给人类提供了食品、木材及其他产品。如果没有树，动物无法在地球上生存下去。

Secondly, trees can give us shade. On a hot summer day, people can have a rest under the shade of a tree after they have walked a long way.
其次，树给我们树荫。在炎热的夏天，人们在走了很长的路后可以在树荫下休息。

Thirdly, trees help to prevent drought and floods. If we cut trees down in large numbers, we will lose the best friends in the world.
第三，树有助于防止旱灾和水灾。如果我们大量砍伐树木，我们会失去世界上最好的朋友。

词义解析：

1.useful：有用的
2.provide：提供
3.product：产品
4.animal：动物
5.firstly：首先
6.secondly：其次
7.shade：树荫
8.rest：休息
9.thirdly：第三
10.prevent：组织
11.drought：干旱
12.flood：洪水
13.lose：失去

词组解析：

1.provide… with…：提供…… ……
2.have a rest：休息
3.cut down：砍伐