The correct answer is D.
US economic recovery after the Great Depression was mostly based on goverment-driven economic policies that sought to increase aggregate demand figures and employment levels. This is why the sucessful package of measures known as New Deal, and based in Keynesian economic principles, was introduced by President Roosevelt. It aimed to increase aggregate demand and employment by increasing goverment spending to start public works projects.
Moreover, the need to manufacture military equipment and other materials for WWII, increased national output, income and employment figures.