To accurately answer your question, I would need to see the map you're referencing, as the areas labeled A, B, C, and D are not defined in the text of your question. However, I can give you some general information about the United States' territorial acquisition from France in 1803, which is known as the Louisiana Purchase.
The Louisiana Purchase involved the acquisition of a vast territory that stretched from the Gulf of Mexico to Canada, and from the Mississippi River to the Rocky Mountains. If you have a specific map, the area that corresponds to this description would usually be the one indicated as the Louisiana Purchase.
If you can provide more details about the labeled areas or a description of what they represent, I can help you determine which area corresponds to the Louisiana Purchase.