I know Mr. Brown; we to each other at an international conference.A. are introducedB. ar

问题补充：

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

A. are introduced

B. are been introduced

C. were introduced

D. had been introduced

答案：

A. are introduced

B. are been introduced

(答案→)C. were introduced

D. had been introduced

解析：由前句：know，说明introduced为以前的被动。