人教新目标九年级下Unit13 we' re trying to save the earth!Section B （self check）课文练习含答案
三、用所给动词的适当形式填空。
1. We are trying (work) hard at all the subjects.
2. There used to (be) a lot of manatees. But now there are few.
3. What was the air pollution (cause) by?
4. Have you ever (throw) away things you don't like to use?
5. I have also (set) up a website to sell clothes online.
6. Mark (work) in China for 10 years and now he teaches Chinese in Britain.
7. What would happen if he (go) back home late?
8. Can the book be (bring) back to my room?
9. --Why not (buy) John a toy car for his birthday?
--Good idea! He is crazy about cars.
10. The math problem is so hard. I really don't know how (do) it.