Ⅰ、Choose the best answer.(选择最恰当的答案，用A、B、C或D表示填入括号内) （共20分）
( ) 1. --What did the teacher tell us _______ just now?
--Not to make anything in the classroom dirty.
A. do B. to do C. doing D. did
( ) 2. We should make a contribution to ________ our country stronger and safe.
A. make B. made C. makes D. making
( ) 3. There are ________ students in our collage.
A. six hundred B. six hundreds
C. six hundreds of D. six hundred of
( ) 4．Welcome to Hangzhou，Mr Baker．It's the first time you visit this city， ？
A．isn't it B．hasn't it C．do you D．will you
