What he said and what he did _____ quite different.

The university estimates that living expenses for international students________around $8,450 a year，which________a burden for some of them.                     (2013·湖南，33)

I took mathematics and physics because I think that ________ very important for me to make further research in this field.

He read more books than she ________. So he had more knowledge.

Nowadays signs prohibiting smoking       a common sight in restaurants, tea houses and shopping malls．