It sure isn't D. One of the reasons the South had trouble during the civil war is that she didn't have enough rail lines. Horses did much of the work the rails did.
The rails existed in 1865. There were lots of them. Trouble was they were mostly in the North.
The large population centers were largely in the east. Shear numbers would make rails feasible. Answer
The West did oppose the rails to some extent, but industry (like cattle and mining) wanted more rails. Most of the time the opposition came for economic reasons.