Answer:
c.the Central Pacific Railroad
Explanation:
The first transcontinental railroad in the United States is the name of a railroad line across the United States that linked the city of Omaha (Nebraska) with Sacramento in the 1860s, thus linking the railroad network of the Eastern United States with California, on the Pacific coast. It ended with the famous Golden Spike ceremony held on May 10, 1869 in Promontory (Utah), creating a nationwide mechanized transportation network that revolutionized the population and economy of the American West. that the famous wagon trains (wagon trains, in English) of the so-called old west of previous decades became obsolete, changing them for a modern transport system.
Authorized by the Pacific Railroad Act of 1862 and strongly supported by the federal government, it was the culmination of a movement over decades to build this line and was one of the greatest achievements of the presidency of Abraham Lincoln, completed four years after his death. The construction of the railroad required enormous feats of engineering and work to cross plains and high mountains by the railroad companies Union Pacific and Central Pacific, the two companies that built the line to the west and east respectively.