There is so much noise in the next room．I wonder__________________．（ ）
A．what are they doingB．what were they doing
C．what they are doingD．what they were doing
The telephone _______ by Alexander Graham Bell．（ ）
A．was inventedB．invents
C．invented
I _______ Anna since three years ago．（ ）
A．knewB．knowC．have known
If I go to the movie， I _______ my homework on time．（ ）
A．didn't finishB．don't finish
C．won't finish
I like Chinese， _______ I don't like math， because it's not easy to learn it well．（ ）
A．andB．butC．or
I think it's impolite _______ others waiting．（ ）
A．to keepB．keepingC．keep