A、In a library. B、In a book shop. C、In a restaurant. D、In a department store. A根据选项，推测提问是关于对话发生的场所，对话中谈到了借书的一些规则，据此可以判断答案是A

W: Whereas European nations have traditionally employed metric units such as meters and grams, the U.S. has employed English units such as feet and pounds.
M: Both systems are now in use in the U.S., though.
Q: What are the two people talking about?

W: There is a limit of three books for each person. Do you still want to have them?
M: Fine, thanks. I’ll be certain to return them on time.
Q: Where did this conversation take place?