听力原文:W: Were you able to use the book that Dr. Nelson put on reserve for our homework?
M: No, I wasn't. It's a mystery to me why the library closed early.
What does the man mean?
A.The library no longer had the book on reserve.
B.The library closed earlier than he'd expected.
C.The professor had chosen a mystery book for him instead.
D.The homework assignment isn't clear.