【单选题】

听力原文：M: Good morning. Say, do you know what the homework is for our term paper in history?

W: Sure. You weren't in class on Monday, were you? That's when it was given out.
M: No, I missed that class. Was there a handout?
W: No, the professor just wrote the assignment on the board (20) .
M: Could you lend me your notes?
W: Yes, of course, but I just wrote down the part that I wanted.
M: Oh, no.
W: You see, there were four choices of topics for the term paper (19) . But when 1 saw them, I knew which one I wanted so I didn't copy the other three (21) .
M: Can you remember any of the others7
W: Let's see. There was one about World War I, but I don't remember the details, and there was one called 'The Idea of' Progress in the Nineteenth Century'.
M: And what was the last one?
W: I can't remember. My mind is a complete blank. Maybe you can ask someone else.
M: Yes, I will Anyway, those topics are quite broad.
W: Yes, but you can focus on a special area within them. Which one would you take?
M: of course, I don't know what the last one is, but of these three, I think I’d take 'the idea of progress'.
W: That's very abstract.
M: But it's one of my interests and I have read a lot on the subject (22) . I've never written a term paper on it though.
W: Me neither. I haven't even read about it. Are you going to class on Wednesday?
M: Yes.
W: Maybe the professor will talk about the assignment again.
M: I hope so. Good luck with your paper.
W: Thanks. Same to you.
(23)
A．Three.
B．Four.
C．Five.
D．Six.