The answer is indeed letter B. To indicate whether the library owns a particular book.
Explanation:
A catalog is a list of items ordered in a systematic manner (alphabetically, for example). A library catalog lists the bibliographical material that can be found in that library. That, of course, includes the books the library owns. It can, however, have other sorts of bibliographical items, such as maps, graphs, realia etc. Having that explanation in mind, the best option among the ones given in the question is letter B - the purpose of a library catalog is to indicate whether the library owns a particular book.
