【正确答案】
C
【答案解析】[听力原文]6-7
M: Hi! I think we've met before. It's good to see you again!
W: Hi, how are you?
M: Fine, thanks. Er... must be a couple of years since we last met?
W: Oh, even longer -- four years ago, I think. In Miami, wasn't it?
M: Yes! Yes, that was an interesting conference!
W: Yes! I remember that after it we visited this city together.
M: And took pictures together, it's such a good memory.
6. When did the two persons meet last time?
由“four years ago，I think．”可得出答案。