The correct answer is: "The American System promised to help transport crops to northern markets."
The American System was proposed by Henry Clay during the first half of the 19th century. It was an economic planification which had three main pillars: setting tariffs to protect the US national industries, the creation of a national bank for supporting commerce and the use of federal subsidies to build cannals, roads and to foster transportation in the general with the ultimate goal of enabling the creation of profitable markets for agricultural products.
Clay believed that the Southern states would support the plan because of this latter proposition, as connecting their cotton supplies with Northern markets, would make their agricultural exploitations more profitable. But in reality, Southern states did not really support the proposal,
