How Did the McCormick Reaper Help the North When the Civil

How did the McCormick reaper help the North when the Civil War?

A) It forced the South to invest more and more into slavery to keep up production
B) It proved to the border states that the North was technologically more advanced.
C) It allowed the North to keep agricultural production high even though many farmers went to fight.
D) It ensured that France would remain pro-North during the war.
E) It enabled the North to grow more corn than the South.