If the north could get control of the Mississippi River it would cause several problems for the south

Control of the Mississippi River gave strategic advantage to the side that had it. That´s the meaning of the Battle of Vicksburg in 1863. With Vicksburg in its hold, the North could control all the navigation, trade, people´s movement, impede smuggling of arms, food and weapons for the Confederacy, and the South stayed divided into two halves (a military disadvantage). That´s why the Confederate president Jefferson Davis said that it was "the key to the South." After the fall of Vicksburg and the crushing defeat in Gettysburg, the Confederacy cause was practically doomed, it was a matter of time for its final defeat.

Explanation:

c. is the answer : ) (you may punch me if im wrong lol)