It is D. It contrubted to the opening of the western frontier.
The railroad leaders consolidate their lines in the 1880s to reduce competition and increase efficiency. Thus the correct option is A.
The railroad is referred to as a mode of transportation that plays a crucial role in transferring people from one location to another. These enable the movement of people as well as performing trade-related activities at a cheaper cost.
Two roads—Northern and Southern—were put out, and this disagreement correlated with the larger conflict between the North and the South. The railways established offices and dispatched representatives throughout the East and Europe in an effort to entice people to live on these territories.
Railroad building in the US developed quickly starting in the early 1870s. As railroads expanded in the West, markets in the East were interconnected. Therefore, option A is appropriate.
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the west is the answer i just got the answers for this test