Among the given choices, the sentence fragment is b. Books, papers, and folders in a stack on the desk.
Sentence fragment are called as such because fragments are found in incomplete sentences. Fragments cannot stand on its own. It does not convey a complete thought. Fragments must be connected to an independent clause to form a complete sentence and convey a complete thought.
In the sentence fragment <em>books, papers, and folders in a stack on the desk</em> <em>, </em>it does not give a complete message because it gives rise to the question What? What about the books, papers, etc?
