3. 树木可以有助于保持水土。

2. 垃圾应该被分为不同的类别。

四、完成句子

1. 那场大雨并没有影响到比赛。

6. —Why didn't you answer my telephone yesterday?

  —Oh,sorry. I (wash) my hair.

5. (chat) with others on the Internet wastes too much time.

4. Air pollution makes people (feel) uncomfortable.

3. Don't you think it fun (skate) with your family in winter?

2. People should do what they can (stop) wasting.

三、动词填空

1. Swimming skills (teach) in our school next term.

10. — What the accident,do you know?

   —I heard a little boy rushed onto the road suddenly.