A、In only one semester. B、In just two semesters. C、In at most three semesters. D、In at least four semesters. C选项中重复出现的semesters表

M: Good morning, Dr. Smith. My name is Peter. I am a freshman in your department. There are a few things that I am not quite sure of and I do need your advice.
W: Thank you very much for your trust, Peter. As your academic advisor I will try my best. Just tell me how I can help you, Peter.
M: I used to major in English, but now I have made up my mind to switch to Applied Linguistics, concentrating on Teaching English as a Foreign Language. It will probably take me two years to get my master’s degree since I also work part-time.
W: So you want to switch majors?
M: Yes. But I have been wondering if it is possible.
W: Well, usually we allow it, as long as you have enough credits.
M: That’s good news for me. I’m not interested in literature and that sort of thing. I want to be a real teacher, Professor. Actually, teaching is what appeals to me, but I’m worried about the make-up credits. I have been taking a lot of courses in English.
W: You usually do have to make up some credits when you switch majors. Are you OK on credits?
M: Not too many. I’ll have to add about 12 credits as far as I can figure from my transcript. Would you please let me know how many credits are required to get a master’s degree?
W: Usually 36 credits are needed. If you take five courses per term, you’ll have enough credits after just two semesters. Usually each course is worth three credits. To get the six remaining credits you either prepare a thesis or take two more courses.
M: I’m afraid I might find that course load a little too heavy. But now I have a clearer idea. Thank you very much for your help, professor.
W: Well, many students carry a lighter load, especially in the first term.
M: Is there anything else besides the 36 credits for the master’s?
W: You have to have an oral defence.
M: I see. All this about credits was so complicated but now I have more confidence. I really appreciate your help, professor.
W: Glad I can help. Good luck, Peter.
Questions 19 to 22 are based on the conversation you have just heard.
19. Why does the man resort to the woman?
20. What is the woman’s profession?
21. Why does the man want to take up Teaching English as a Foreign Language?
22. How soon could the man get a master’s degree if he takes four courses per term?