--- Is that man Mr. Smith?--- It ______ be him. He has gone to NewYork on business.
---He went to see the man who was in hospital yesterday.--- ______.
---I _________ stay up late. ---Really? I didn’t. But I ______ working in the night.
Beijing _________a lot in the last ten years. It is one of _________ in China.
We really don’t know _________ with our problems in learning English.
They were walking ________ a forest after they swam _______ the river .