The correct answer is “Spain closed the port in anticipation of the French's arrival and to cut off American traffic from its markets.”
During the Spanish rule over Louisiana and New Orleans Spain made a secret treaty with France and agreed to trade Louisiana, they decided to trade because they could not keep Americans out of the territory. Before they handled the territory to France, Spain closed the port of New Orleans to American shipping. Because of the importance of New Orleans to the American trade, President Thomas Jefferson asked France to buy New Orleans. Napoleon who was the French ruler at the time needed money because of the war with the British and offered the Louisiana Purchase.