Final answer:
The Chisholm Trail led to the cow town of Abilene on the Union Pacific railroad, which is the correct answer to the question and is option A.
Step-by-step explanation:
The Chisholm Trail was a route used for driving cattle from Texas ranches to Abilene, Kansas, for shipment to markets in the East. The key rail line in Abilene was the Union Pacific Railroad, which, along with the Central Pacific, completed the First Transcontinental Railroad in 1869.
The trail and railway were central to the operations of cattlemen like Joseph G. McCoy, who significantly contributed to developing Abilene into a thriving cow town.