The area that the United States purchased from France in 1803 is known as the Louisiana Purchase. The Louisiana Purchase encompassed a vast territory, which includes parts of several states today.
Without seeing the map, I cannot identify the areas labeled A, B, C, or D. However, the correct answer should correspond to the area that is recognized as the Louisiana Purchase on your map.
If you have access to the outlines of the areas labeled A, B, C, and D, the correct answer will likely be the area that represents a large portion of territory west of the Mississippi River, which was acquired from France in 1803.