A、He can’t find his office key. B、He has misplaced some exams. C、He is unable to speak out. D、He doesn’t enjoy teaching. C①所有选项都

M: Math Department, Doctor Webster speaking.
W: Hello, Prof. Webster, this is Janet Hill calling, I live two doors down from your teaching assistant, Don Williams. [1]Don asked me to call you because he has lost his voice and can’t talk to you himself.
M: Oh, what a shame! Is there anything I can do for him?
W: Well, he has a class this afternoon from two-thirty to four and he won’t be able to teach it, but he doesn’t want to cancel it either.
M: Want me to try to find somebody else to teach the class?
W: No, not exactly. [2]What he wants to do is to get someone go in for him, just to pass back the midterm 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 two-thirty, eh? Well, at that time I was going to be on campus anyway; so I could do it for him. What room is his class in?
W: Cader Hall, Room 214. [3]Will you need his office key to get the exams? He’s given it to me and I could bring it to you.
M: Actually, that won’t be necessary. We have a master key in the math department. So I can get into his office.
W: Thank you very much, Prof. Webster. Don doesn’t have another class to teach until Thursday, and hopefully, he will be able to talk by then. He’ll call you as soon as he can.
M: Anything else?
W: Oh, yes, I almost forgot. Could you put the next assignment on the board, too? [4]It’s all the problems on page 45, and they are due at the next class.
1. What is Don’s problem?
2. What favor does Don want someone to do for him?
3. What does Janet offer to do?
4. What do the students have to do before seeing their teacher next time?