Why Was the Expansion of Railroads Significant to the Growth

Why was the expansion of railroads significant to the growth of the cattle industry?

A) As the railroads increased the ability to ship huge numbers of southern cattle, more cow towns were established in the West.
B) The railroads enabled the meat of eastern cattle to be shipped west in order to feed the region's growing population.
C) The railroads opened up Mexico as a market for American meat and eliminated the need to maintain cattle ranches in the United States.
D) Cowboys from the eastern states could now travel to the West to apply their expertise and teach new settlers their ways.
E) The railroads increased the industry's profit margin by eliminating the need for cowboys, and ranches were converted to modern-day factory farms.