Frank looks very worried today. There must be ________ wrong with him.

（2007年浙江省第二次五校联考，8）How long do you think ___________ the Microsoft brings out a new product?

_______ did the meeting last? —For two hours.

This TV play is very interesting．Why _________ down and watch it?

Our English teacher is often _______ to give a talk on English study. He is popular.