Answer:
C. Immigrant labours.
Step-by-step explanation:
Chinese Workers Dominated the Workforce. Chinese laborers at work with pick and shovel wheelbarrows and one-horse dump carts filling in under a trestle built in 1865 as part of the transcontinental railroad. Irish immigrants, freed slaves and Mormons also worked on the transcontinental railroad. Snow fell so deeply that they had to build roofs over 37 miles of track so supply trains could make it through. The conditions were merciless, dangerous and harsh.