A、None. B、Once. C、Twice. D、Four times. D根据男士的回答“four summers”可知，男士去野营四次了，故选D。

M: What are you going to do after your return from New York?
W: I’m going to stay in the city.
M: What will you do all day?
W: I’m going to work with my father at the workshop. In the evening, I’ll read books. (18) On weekends, I’ll go to the park with my family.
M: Have you ever worked?
W: No, but I can learn. What are you going to do this summer?
M: I’m going to camp. (19) I’ve gone to camp for four summers.
W: I’ve never gone to camp. What do you do there?
M: We do many things. In the morning, we go swimming and boating. In the afternoon, we play volleyball or tennis. We sit around a campfire at night. We sing or tell stories.
W: That sounds wonderful.
M: It is wonderful. What’s Wales going to do this summer?
W: I think he’s going to the mountains with his parents.
M: Well, so long, Alice. Have fun.
W: You too, Leslie. Give my regards to Wales. I’ll see you in October.
17: What is the possible relationship between them?
18: What is the woman going to do on weekends?
19: How many times has the man gone to camp in summer?