We have already (发射) spaceships to Mars.
Liu Chuanjian is considered a (英雄)because he safely landed the damaged plane.
Who is (敲)at the door?
Maybe it's the postman.
I can't hear you (清楚地). Please speak a little bit louder.
I met a friend of (她的)in the street yesterday.
Drinking too much juice can be (有害的) to people's teeth.