Why were the straits between the aegean and the black seas so important to the byzantines?

Ive been stuck on this question! which of the following statements about the economic consequences of the civil war is not accurate. a. inflation caused prices to rise by 80% in the north. b. because southern farms could not produce enough food for everyone in the south, the union navy allowed food shipments from britain. c. to pay for all of the food, supplies and armaments that were necessary for the union army, congress instituted an income tax. d. business bloomed in the north as factories and farms always had a market for the products.