The correct answer is D) receiving government aid.
A legal means that the builders of the transcontinental railroad used to cut costs and finance railroad construction was receiving government aid.
The Pacific Railroad Act of 1862 authorized the construction of the Transcontinental Railroad that connected the East of the United States with the Pacific West. The companies in charge of the project were the Union Pacific company and the Central Pacific. They worked for seven years to connect the railroad from Sacramento, California to Omaha, Nebraska, until they finally did so on May 10, 1869, in Promontory, Utah.