The transcontinental railroad would not have been possible without constant presidential oversight british loans funding the track a large supply of immigrant labor (irish and german laborers from the east, and primarily chinese from the west) strong leadership from the owners of the central pacific railroad

The correct answer is: a large supply of immigrant labor.

The hard work of the Chinese was crucial in the construction of the railroad, being responsible for 15 tunnels along it.

An Irish foreman would usually be in charge of a tunnel together with about 40 Chinese men. About 15 men worked on the heading and the rest on the bottom of the tunnels.

i normally just use

got any answer choices?