The correct answer is D. American people choose to move west to purchase affordable land and farm it themselves.
These first settlers of the American West were called Pioneers. Their main motivation was the accessibility of lands, thanks to laws such as the Homestead Act. Thus, the American West was populated by brave pioneers who left their lands to settle and seek prosperity in territories that until then were depopulated. The immigration to the West was creating the great metropolitan areas that we find today in the American West, like Phoenix, Tucson or Denver.