词性转换：
1. It's often __________(rain) in spring here.
2. Sometimes people __________ (pollution) the Earth and leave rubbish everywhere.
3. Some people think "13" is an __________ number. (luck)
4. Tony wants to have two __________ (secret) to help him with the work.
5. Some people don't throw rubbish in the bin. They are _________ the earth. (pollution)
6. We promise _________ (plant) more trees and flowers to make our environment beautiful.
7. The boys are going out of the classroom _________ (quick).
8. I want _________ (be) a policeman when I grow up.
9. Why not use your dictionary? It's very _________ (help).
10. I like to eat some rice and a lot of _______ (boil) vegetables.
11. How many _______ have you got? (potato)
12. Excuse me, but where is the _______ (enter) of the hall?
13. There is so much noise _______ (pollute) to live near the airport.
14. Please don't talk _______ (loud) in the meeting room.
15. Tomorrow will be Lucy's birthday. Have you got her _______ (invite), Alice?
16. Sam has a good diet now. He is _______ (healthy) than before.
17. It’s raining outside. How about _________ books now? （read）
18. We learn something about the air ___________ from the books. （pollute）
19. Our teachers are very _________ to us, so we like them very much. （friend）
20. The two __________ from America will visit our school next week. （family）
21. Jack is ___________ a visit to the Great Wall. （plan）
22. Both his father and brother are ____________. （fire）
23. The two blue ____________ on your left are our dormitories. (build)