Paperback books wear out more quickly than hardcover books do, but paperback books cost much less. Ttherefore, users of public libraries would be better served if public libraries bought only paperback books, since by so doing these libraries could increase the number of new book titles added to their collections without increasing their budgets. Which one of the following, if true, most seriously weakens the argument? ['People are more likely to buy for themselves a copy of a book they had previously borrowed from the public library if that book is available in paperback.', 'Library users as a group depend on their public library for access to a wide variety of up-to-date reference books that are published in hardcover only.', 'Paperback books can very inexpensively have their covers reinforced in order to make them last longer.', "If a public library's overall budget is cut, the budget for new acquisitions is usually cut back more than is that for day-to-day operations."]