听力原文:W: Professor Johnston has been very busy this month. I've heard that he stays up
M: If I had known this I wouldn't have troubled him so much.
Q: What do we learn from the conversation?
(19)
A.The man took up much of the professor's time.
B.The man didn't make any trouble with Prof. Johnston.
C.The man has trouble getting along with Prof. Johnston.
D.The man knew Prof. Johnston was very busy.