Train service suffers when a railroad combines commuter and freight service. By dividing its attention between its freight and commuter customers, a railroad serves neither particularly well. Therefore, if a railroad is going to be a successful business, then it must concentrate exclusively on one of these two markets.
For the argument to be logically correct, it must make which one of the following assumptions?
OPTIONS
[A]. Commuter and freight service have little in common with each other.
[B]. The first priority of a railroad is to be a successful business.
[C]. Unless a railroad serves its customers well, it will not be a successful business.
[D]. If a railroad concentrates on commuter service, it will be a successful business.
[E]. Railroad commuters rarely want freight service as well.

Why the answer is C) and not A)