A. It encouraged expansion by granting low-cost land to settlers
The development of the automotive industry has opened many jobs worldwide, including in the USA.
The automotive industry has a vast production chain, involving the plastics, steel, and car components industries. In this sense, besides the direct jobs, there is a great indirect employability.
In this context, the popularization of automobiles has increased the contingent of workers in related industries, as described in the third alternative (C).