Option D is most appropriate.
We see one of the major effect of The Great Depression was widespread unemployment. There were more than 10 million people unemployed in the US. So resolving unemployment was main issue of New Deal. Under New Deal we see The Civilian Conservative Corps ( CCC ) was created which employed 2.5 million young men on conservation and reforestation projects.
So in between The Great Depression and The New Deal, widespread unemployment suits the most. The Unemployment was an effect of The Great Depression and a cause of  establishment of New Deal as well.
