------- Jack, you erase the blackboard today, __________?

------- But I did it yesterday.

Open a window,________?

A.wouldn’t you             B.won’t you                 C.would you                 D.don’t you

Only when you have obtained enough data ________ come to a sound conclusion.

         A．can you      B．you can      C．would you    D．you would

---Jack, you erase the blackboard today, __________?

---But I did it yesterday.

A. will you                       B. do you     C. would you            D. don’t you

You’d never heard of it before I told you,________?

A.did you                     B.didn’t you                 C.would you                 D.had you