Microblogs experienced rapid growth in 2011 in China, with the number of microblog operators, users and visitors _____ several times.

Will you be available at three o’clocktomorrow afternoon – No. I ______ a lecture then.

I’m afraid you missed a fantastic lecture yesterday. How come you were absent from it?—If you _______ know, I asked for a day off and visited a relative of mine in hospital.

You are asked to attend the meeting ______ in the hall this weekend.

Peter is not himself these days. —Well, could you tell me________