Final answer:
The letter that represents the Battle of Yorktown is 'A.' The geography of Yorktown, with its peninsula location and the presence of French naval forces, led to Cornwallis's defeat.
Step-by-step explanation:
The geography of Yorktown played a crucial role in Cornwallis's defeat. Yorktown is located on a peninsula formed by the York River, Chesapeake Bay, and James River, making it difficult for Cornwallis to escape by sea. Additionally, the French Admiral de Grasse sailed his naval force into Chesapeake Bay, blocking Cornwallis's escape route. This forced Cornwallis's army to be surrounded and ultimately led to their surrender.