Answer:
B. Full control of the Mississippi River for quicker trade
Step-by-step explanation:
Without a doubt, one of the main geographical advantages that the U.S. obtained with the Louisiana purchase was the complete control of the Mississippi River, and the rest of its basin.
This was important because the Mississippi is a very large river that can be easily navigated during most of the year, something that made trade easier. Besides, the land around the Mississippi river is some of the most fertile in the world, specially in the areas around what is now Iowa and Illinois, two states that are part of the agricultural hinterland of the United States.