A、Two. B、Four. C、Six. D、Five. C对话中最后谈到old Jake，his wife，his daughter，Dr. Thomas，his wife，his daughter，共六个，因此答案是C。

A: Bob, do you know who I saw the other day? Old Jake, looking terribly depressed. Did he get his pension at last?
B: Yes. They made him stop working after 50 years at sea. He’s pretty upset about it, but what can you do? He has to accept that.
A: He’s all alone, isn’t he?
B: Yes. His wife’s been dead for years. They had one daughter, Doris, but she went off to town as soon as she left school, and he hasn’t heard from her since. I hear she’s making good money as a model.
A: Maybe someone should get in touch with her, get her to come back for a bit to help?
B: I don’t suppose she’d come. She never got on with her father. He’s a bit of a tough character, and she’s as selfish as before. Oh, I expect old Jake will get by. He’s healthy at least, comes into the clinic for a check regularly.
A: Are you his doctor?
B: No. My colleague, Dr. Thomas is.
A: That bad-tempered old man?
B: Oh, no. Dr. Thomas is not really bad-tempered. He just looks like it. He’s an excellent doctor. He teaches me a lot. And he has a very nice family--his wife invites me over there to supper every week, very pleasant.
A: I know his daughter, a bit careless but bright and popular with her age-group.
B: I like that little girl, too.