听力原文：M: Hi, Sarah, what's up? W: Oh, hi. I just got out of a history class. I had to give a presentation. M: How did it go? W: Terribly. I'm sure I made a fool of myself. M: Why? Weren't you prepared? W: No, it's not that. I just get so embarrassed and nervous whenever I've to speak in front of a group of people. I stand up and my face gets red and then I get even more nervous because I know everyone can see me blushing. M: It is not so bad to blush. W: But it happens all the time. If the professor asks a question and I know the answer, I'll blush like crazy if he calls on me. Doesn't that ever happen to you? M: No, not really. Maybe you should try to forget about the people. Look at something else in the room, like the exit sign. W: I guess I could try that. But I doubt it will help. M: You know we talked about this in psychology class. Blushing, even though it's involuntary, is more or less a learned behavior. W: What do you mean? M: Oh, children hardly ever blush at all. And, among adults, supposedly women blush more than men. W: I wonder why. M: I don't know. But I had a friend in high school, Brian Smith. It was really easy to make him blush. He turned red whenever a waitress would ask him for his order. W: I'm not that bad. Well, I've got to get going for my next class. I'll talk to you later. (20)