听力原文：M: Math Department, Dr. Smith speaking. W: Hello. Prof. Smith, this is Lucy Wang calling. I live two doors down from your teaching assistant, Brain Williams. Brain asked me to call you because he has lost his voice and can't talk to you himself. M: Lost his voice? Oh, what a shame. Is there anything I can do for him? W: Well, he has a class this afternoon, from 2:30 to 4:00, and he won't be able to teach it, but he doesn't want to cancel it, either. M: Does he want me to try to find somebody else to teach the class? W: No, not exactly. What he wants to do is to get someone go in for him, just to pass back the mid-term exams. He's already marked them and they are on the desk in his office. The whole thing wouldn't take more than ten minutes. M: His classes are at 2:30, you say? Well, I'm free at that time. I am going to be on campus anyway. So I could do it for him. What room is his class in? W: Main Building, Room 804. Will you need his office key to get the exams? He's given it to me and I could bring it to you. M: Well, actually that won't be necessary. We have a master key in the Math Department, so I can get into his office if necessary. W: Thank you very much, Prof. Smith. Brain doesn't have another class to teach until Thursday and hopefully he'll be able to talk by then. He'll call you as soon as he can. Oh, yes, I almost forgot. M: Yes? W: Could you put the next assignment on the board, too? It's all the problems on page 30, and they're due at next class. M: No trouble at all. Thanks for passing on the news about Brain, and please tell him not to worry about anything. (27)