Johnson won't answer the phone if he ___________ the number．（ ）
A．knewB．doesn't know
C．will knowD．didn't know
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
I cleaned my room yesterday． It _______ a little difficult．（ ）
A．isB．wasC．will be
Mountain climbing is one of _______ sports in the world．（ ）
A．dangerousB．more dangerous
C．the most dangerous