It is uncertain ___ side effects these weight-loss drugs will bring about, although hundreds of thousands of patients have taken it.
This passage has too many long sentences. I’m afraid they will be hard for most of the students. Could you help to _______ them?
The police are to ______ the traffic accident that we don’t know _____.
— The floor is dirty. — Yes. It _______ for two days.
My sister_____ Tony for ten years next year.
Do you know a concert _____ in our hometown next month?