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

问题补充：

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

答案：

A. are introduced

B. have been introduced

(答案→)C. were introduced

D. had been introduced

解析：在一个国际会议上被介绍显然发生在过去。