The Works Progress Administration stimulated manufacturing by C) giving workers increased purchasing power.
The WPA created by President Roosevelt in 1935, as a program that intended to decrease unemployment and contribute to overcome the hard times during the Great Depression, achieved to employ millions of people to carry out public works projects, such as school and hospitals buildings, bridges, airfields, reparation of roads, storm drains, sanitary sewer lines, etc.
Most of the people hired were unskilled men, that didn't have any job before. The WPA program provided them decent paid jobs, which eventually increased their purchasing power.