参考答案：B

解析：[听力原文]6-8
W: Do you know where Tom is
M: Sorry, I don’t know.
W: Oh, my God!
M: What’s the matter
W: He is supposed to be at the meeting a quarter later. But I can’t find him anywhere.
M: Oh, I remember something. John told me that Tom went out for lunch at ... er ... about a quarter to two and would not be back unitl 3:30.
W: Then he will be late for the meeting.
M: What’s the time now
W: 3:00.

[精解] 题干问：“对话发生在什么时候 ”对话中分别出现了几个不同的时间，但只有对话最后所出现的时间才是对话发生的时间，即3:00。所以答案选B。