---What do you think of your parents? ---They always let me do ________ I think I should do.
The air in mountain areas is ____ that in big cities.
Beijing is _____ capital of China and it is _____ city with many places of interest.
Recent pressure at work may___ his behavior.
If he starts talking about his past, you will never___ from him.
To our joy, the operation is___ success and the patient is now out of ___ danger.