How did changes to the railroad help American industries grow?

Railroads often owned the right-of-way along the tracks, thus facilitating the sale of land to potential homeowners. Railroads also made it easier to get mail and consumer goods to people who had moved West.

you didn't list the options. however, a few communist countries today are: the people's republic of china, north korea, and cuba.

a. poison gas was sprayed over battlefields by airplanes to weaken enemy positions before major attacks.