The Greatest Economic Consequence of the Transcontinental Railroad Network Was

The greatest economic consequence of the transcontinental railroad network was that it

A) enabled farmers to make a highly profitable living by shipping their goods across the country.
B) enabled people from farms and small towns to visit the big cities.
C) united the nation into a single, integrated national market.
D) made it possible for some immigrants to settle in the West.
E) developed a skilled industrial workforce.