Each player of chess is trying to trap the other player’s king into a position _________escape is impossible

The problem lies __________ we are now giving him a fish, not teaching him to fish

A strange thing happened her last night, so she is afraidstaying at home alone tonight.

We find _______ not easy _______ fifty English words in one day.

I saw your mother in the library just now.—It ______ be her. She went to Beijing yesterday.