Exercises of passive voice

This kind of dictionary ___________ well.

He was seen __________ knocked down just now.

The medicine__________ in a dry and cool place.

The Olympic Games __________ every four years

The key __________for locking the classroom door.

Who was the book __________?

---Alice, you __________ on the phone. ---I’m coming.

The thief ___________ by the police already.

Old people must __________ politely.

The big tree __________by my mother ten years ago.