听力原文：M: Math Department, Doctor Webster speaking.
W: Hello, Prof. Webster, this is Janet Hill calling. Don 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 two thirty to four and he won't be able to teach it.
M: Want me to try to find somebody else to teach the class？
W: No. What he wants to do is to get someone to 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.
M: Well, I'm afraid I could do it for him. What room is his class in？
W: Cader Hall, Room Two-fourteen. Will you need his office key to get the exams？ He's given it to me and I could bring it to you.
M: No, thanks. We have a master key in the maths department.
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.
M: OK.
W: Oh, yes, I almost forgot. Could you pat the next assignment on the hoard, too？ It's all the problems on Page Forty-five, and they are due at the next class.
M: I see.
(20)

A. He can't find his office key.
B. He has misplaced some exams.
C. He is unable to talk.
D. He doesn't like his classroom.