求以下英语题答案
将下列句子改为被动语态
10. Who cleaned the room?
11. Where did you see the film?
12. The tigers in the zoo frightened the little girl.

13. They talked about the interesting book this morning.
14. He often looks after his sister.
15. Lily often thinks of her grandfather.
16. The teacherstake care ofthe children.

17. People will laugh at you if you wear that dress.
18. Tom is writing a letter.
19. They have planted 2000 trees in the last 3 years.
20. He was reading a book at this time yesterday.
21. They must finish the work today.
22. We should listen to the teacher carefully in class.