old books

[Saneta]

http://www.english-test.net/toeic/listening/most_of_the_books_in_this_library_are_very_old_arent_they.html

Most of the books in this library are very old, aren't they?
I suppose they can't afford to keep up with the cost of buying new books. - in this right answer there is no info about how old the books in this library are, and who does word 'they' mean in the answer?

Thanks for explanations..

[Beeesneees]

That is the correct answer. The other options don't match the question at all so it doesn't matter that there is no actual info about the age of the books.
they = the people who own and run the library.
_________________
Cheers m' dears!