Đáp án:

 1.Football is played over the world (by people).

2. This house was built (by them) in 1978.

3. That film has not been seen.

4.The flowers are being watered (by them) now.

5. The day of the meeting has been changed (by them)

6. He will be phoned if we have time.

7. Homework must be done (by you) before the class

8. A complaint letter should be written to the manager (by them).

9. The problem wasn't said (by them).

10. His story wasn't believed (by anyone).

11. The walls were painted (by them).

12. All the preparations have been made (by them) before yesterday.

13. A story is going to be told (by them).

Giải thích các bước giải:

 Đây là bị động của các thì:

1. Hiện tại đơn

2. Quá khứ đơn

3. Quá khứ hoàn thành

4. Hiện tại tiếp diễn

5. Hiện tại hoàn thành

6. Tương lai đơn

7. S1+must+be+V(P2)/V(ed)+O+by S2

8. S2+should+be+V(Quá khứ đơn)+O+by S2

9.  Quá khứ đơn

1. Quá khứ đơn

11. Quá khứ đơn

12.Hiện tại hoàn thành

13.Tương lai gần