What does webster mean when he says the strength of america will be in the valley of mississippi?

Webster was referring to the thought of cutting the Mississippi river in two by southern states seceding from the union, thereby effectively cutting the Mississippi river into a northern portion controlled by the union and a southern portion controlled by the confederate states. Webster also stated that he would rather hear talk of war, pestilence and famine than to hear talk of secession.

An attractive economy.

The answer should be d.