单项选择题

[听力原文]9-10
W: Now, Mr. Sun, did you see the accident clearly
M: Oh, yes. I was standing outside the post office.
W: Can you remember what time it happened
M: Yes, it was 4:25 by my watch.
W: Good. Now, was the truck going fast
M: Yes. Well, perhaps the driver thought the traffic lights were going to change to green. But they were red.
W: Are you sum, Mr. Sun
M: Yes, absolutely sure.
W: Well, thanks a lot, Mr. Sun. Good-bye.
M: Good-bye.

What are the two speakers talking about（）

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