Answer:
C. Prohibited discrimination in the defense industries.
Railroads were far more effective at transporting goods across the country without the risk or delay that comes with sailing. Canals while effective weren't as speedy or reliable as a train since boats are rather fickle things. The turnpikes were being used by wagons and carriages that I doubt could compete with Trains!
Try to use socratic for these type of question the answer is most likely found there