Imagine you manage a bookstore. The store sells both fiction and nonfiction titles, but because your store is located in a beachside town, it has a very large selection of beach and sea-themed books.
i think that your current answer is good, but before that you should add "since the bookstore is selling sea-themed books, that is what they specialize in."
Explanation:
this sounds right because it is what they specialize in.
