Đổi các câu sau thành câu bị động 
1. You must return those books to the library soon.
2. Did you do your exercises perfectly ?
3. Do they prepare their lessons carefully ?
4. Who has written that novel ?
5. People play football all over the word.
6. My sister is writing that note in her notebook.
7. They keep those maps on the shelves for reference.
8. They have just told us about that.
9. They gave my little sister a ticket.
10. People say he is jealous of her.