A、His major. B、High salary. C、His preference. D、His tutor’s advice. C细节题。根据对话可知男士慢慢意识到自己非常喜欢动物，甚至超过了对人的喜欢，也就是说男士对动物的喜爱使他成为了一名兽医。

W: Now you’ve been an animal doctor for some thirty years. What was it that made you choose this job?
M: Well, I studied as an ordinary doctor in the beginning, but I slowly realized that I liked animals very much. I almost prefer animals to people. So I took an extra course in animal medicine.
W: And you still enjoy working with animals?
M: Oh, yes, very much so. In fact, more than ever now. I’ve got to know animals much better, and I get on better with them. Their owners sometimes get on my nerves, though.
W: Oh, why is that?
M: Some people know very little about animals and keep them in the wrong conditions.
W: What sort of conditions’?
M: Well, you know, some people buy a large dog and try to keep it in a small flat; they don’t take it out enough or to give it proper exercise. A lot of people don’t feed their animals properly. They give pets too much food or not to feed them regularly, which are equally bad for them, especially if they’re not getting enough exercise. Keeping an animal is a responsibility which is something many people don’t seem to realize.
W: You mean people keep pets for the wrong reasons?
M: Yes, some people want a pet because they’re lonely, or even simply to show how rich they are.
W: And just how do you deal with these people?
M: Well, I try to tell them what the animal needs, what is the right sort of food, the proper exercise. I try to teach them that animals are not toys and if they’re to be healthy, they have to be happy.
W: Yes, I suppose you’re right.
Questions 12 to 15 are based on the conversation you have just heard.
12. What makes the man work as an animal doctor?
13. What is some people’s wrongdoing with their animals?
14. According to the animal doctor, why do people keep pets?
15. What’s the possible relationship between the two speakers?