He spent one day ________with his friends.
We know the boy _______ father works in the police station.
This is the topic _______ we are talking about now.
Mrs. White doesn’t know her friend _______ to Beijing. If she _______ here, she will meet him at the station.
Chinese is one of ______ subjects in our school.
I was watching TV ______ my mother was writing an e-mail to her friend.