On a separate page at the end of the document. As with most citation styles, they always appear at the end of the document for easy reference once the reader has finished and wants to refer to your sources. There are no styles that call for it at the beginning of the paper.
The correct answer is A.<span>could not be heard above the voices in the hallway </span> B is a subject, C is an adverbial of reason, while D is an adverbial of manner.
