A、Internet. B、Physics. C、Industrial Revolution. D、History. C细节题。男孩话中有说“I wanted to get those books on industrial revolution．"可判断

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 have been embarrassing. But why did not 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.
Questions 9 to 11 are based on the conversation you have just heard.
9. When did Doctor Brown’ s class finish?
10. What books did the man want to get?
11. What did the librarian think?