The correct answer is C) It would stop supplies from reaching the South.
Northern strategists viewed the Mississippi River and its tributaries as vital to a Union victory in the Civil War because it would stop supplies from reaching the South.
The Union Army knew that if they were capable of defeating the Confederates and control the Mississippi River ports, they could stop supplies from reaching the South. Without supplies, it was just a matter of time to gradually debilitate the Confederate Army.
That is why the victory and control of Vicksburg, Mississippi was so important for the Union. On July 4, 1863, Confederate General John Pemberton surrendered the city to Union's General Ulysses S. Grant.