【正确答案】 A

【答案解析】[听力原文]
   M: Do you know what happened to me today? I was so embarrassed.
   W: What?
   M: Well, Dr. Brown's class finished 10 minutes early, so I went to the library between classes. I knew I didn't have much time, but I wanted to get these books on the Industrial Revolution. I looked them up in the card catalogue and went right to the stack and found them. So I put them in my book bag and headed back towards the door. Then it happened. The exit gate in front of the door wouldn't open, and the guard immediately warned me that I hadn't checked out my books. He thought I was trying to steal them.
   W: That must've been embarrassing. But why didn't the exit gate open?
   M: I asked them that. It seems that the books in the library are all magnetically coded, and when you check them out, the librarian behind the desk demagnetizes them, then the exit gate will open.
   W: How interesting! I still don't quite understand how they do it, though. I'll have to go to the library and see it for myself.
   Why did the man decide to go to the library?
通过选项中提及的classes，studying，library，overdue等词可以推测对话涉及图书馆中发生的一些事情，或者是某人学习需要借书等，所以在听音时需要注意到底是谁需要借书，借书的程序是什么，以及具体发生了什么。男生说因为今天Brown博士提前十分钟下了课，所以他就在课间去了图书馆。所以A正确。