Why did Jefferson worry about the impact of European conflict on the Mississippi River?

He believed the river was key to gaining control over Florida and other Spanish colonies.
He feared the river would be used to establish a border among the British, French, and Spanish colonies.
He feared the war in Europe would result in the United States losing trading rights at the Port of New Orleans.
He believed that if the Spanish regained control over the river, the United States would have to enter the war.