I know Mr Brown； we ＿＿＿＿＿＿ to each other at an international conference.

A.are introduced     B.have been introduced

C.were introduced     D.had been introduced

I don’t like talking on＿＿telephone；I prefer writing＿＿letters．

 A．a； the    B．the； 不填 C．the； the D．a； 不填

I know Mr. Brown；we ＿＿ to each other at an international conference.

A. are introduced                       B. have been introduced

C. were introduced                      D. had been introduced

I as well as my friend ＿＿＿ the same opinion that one day or two ＿＿＿enough for this work.

— Has Jack finished his homework yet?

   — I have no idea；he ＿＿it this morning.

A. was doing    B. had been doing    C. has done      D. did