A)Students with a library card can check any book out.
B)Reference books are not allowed to be checked out.
C)Only students with a library card can check out reference books.
D)The number of books a student can check out is unlimited.
原文：
M: I thought the librarian said we could check out as many books as we need without
our library cards.
W: That's right, but not those reference books.
Q: What does the woman mean?