The correct answer is World War II.
Even though the New Deal, implemented by FDR during the Great Depression, helped tremendously by lowering the unemployment rate and helped banks to recover, the real reason the US escaped the Great Depression was World War II.
The increased call for weapons, resources, and materials needed for war resulted in an increase in the amount of workers needed. Along with this, the military draft resulted in millions of men leaving their jobs at home to work for the military. This allowed women and African-American men to take over these roles. With the increased production needed to sustain the war effort, the unemployment rate plummeted and America's economy prospered greatly.