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
网友回答
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。