Which industry benefited the most from the construction of railroads in the post civil war period?

a. Agriculture

b. Banking

c. Steel

d. Mining

I feel like that is almost definitely Agriculture. For one, it just makes logical sense because railroads = industrialization and industrialization = more people (aka more crop output). But if you need to examine it more, it's obviously Agriculture because now farmers could sell their crop at a national level and not be dependent on the market of their local town.

C, the Steel industry, as railroads were constructed from steel beams.