C. Assuming that for railroad to be successful business, it is required that it serves customers well.
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?
(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.