— I think the man over there must be Bob.— It _______ be him. He has gone to England.
If he _________ here next week, I ____there.
I don’t know _______ .
----I feel tired and sleepy. -----Why not stop _______ ?
If there are ______ trees, the air in our city will be _______ cleaner.
There____ a football game on TV this afternoon .