The correct answer would be C.
Bootlegging Alcohol didn't really give anyone jobs, except allow for members of crime families to gain money. As for Penny Auctions they didn't create jobs for the Americans at that point. The 21st Amendment may of renewed some American spirit, allowing for alcohol to be bought and sold legally, but this didn't provide many jobs.
The best answer would be C, as the construction of the Empire State Building helped grant jobs and helped show the people they've got to keep going. As for the construction of other major landmarks, Hoover Dam, and Statue of Liberty. This gave people a lifted spirit and provided jobs.