We must take care of our children.

=> Our children must be taken care of (by us).

You must clean the wall before you paint it.

=> The wall must be cleaned (by you) before you paint it.

The manager didn't phone the secretary.

=> The secretary was not/wasn't phoned by the manager.

I won't hang these old pictures in the living room.

=> These old pictures won't be hung in the living room (by me).

The German didn't build this factory during the Second World War.

=> This factory was not/wasn't built by the German during the Second World War.

He has broken his nose in a football match.

=> His nose has been broken (by him) in a football match.

*) Nếu trong 1 câu bị động có cả place (địa điểm), by sb/sth (bởi ai hay cái gì), time (thời gian) thì sắp xếp theo thứ tự: place + by sb/sth + time

1. Our children must have been taken care of.

2. The wall must hass been cleaned before you paint it.

3. The secretary was not phoned by the manager. 

4. These old pictures will not be hung in the living room.

5. This factory was not build by the German during the Second World Ửa.

6. His nose has been broken in a football match by him. 

            Chúc bạn học tốt~~