don’t know how it ___________ that our car was bumped from behind.

There is a small object ________ a pin on the desk.[ ]

They moved to Australia_______ 1960. That means they have been in Australia _______ 1960.

In a government work report on March 5, Premier Li Keqiang “declared（宣布） war” ________ pollution.

What troubled the teacher was that no one present made an answer when asked who had broken the glasses, so he didn’t know who .