Đổi các câu sau thành câu bị động 
11. They believed that he was innocent.
12. People know that he is armed.
13. We know that you were in town on the night of the crime.
14. We considered that she was the best singer at that time.
15. They say he was a spy.
16. People rumored that the coming crop was the worst.
17. People say that prevention is better than cure.
18. People believe that he was killed.
19. They reported that the expedition reached the South Pole in May.
20. They have invited all the members to the party.