听力原文：M: Hi. I have some good news for you.
W: What is it？
M: The teacher suggested that we go on a trip this Saturday.
W: Oh, wonderful. Where shall we go？
M: How about going to the park？
W: I don't think it's a good place to go to. We can go there another time. We should go farther away this time.
M: Where do you think we should go then？
W: How about the reservoir in the suburbs？
M: I don't think it's a good idea. It's not safe. Why not go to the mountain instead？
W: That sounds good. Let's go to the mountains to the south of the city.
(18)

A teacher and a student.
B. Classmates.
C. Father and daughter.
D. Mother and son.