His father looks young, but in fact he is ______.

I don’t know what happened _____ Zhang Hong the day before yesterday. [ ]

How can I make full use of my time? —Makea clear timetable first．

Basketball is so popular a game in the world that ______ people play it for fun and exercise.

I think the man over there must be Bob.— It _______ be him. He has gone to England.