Can you explain B pls

@Kostey80, (B) is irrelevant to the argument hence it is not a necessary assumption. Consider the structure of the argument. We are given the following premises: (1) IF RR combines commuter and freight service THEN train service suffers. (2) IF RR divides attention between these two customers THEN neither of the customers are served well. These two premises are basically saying the same thing, if RR combines service, customer service suffers. We can infer that if the RR serves its customers well, then it must be true that it only focuses on one type of service. The argument then concludes that: (3) THEREFORE, IF RR is a successful business, THEN it must concentrate on one of these markets. There is an obvious gap between the premises and the conclusions. The missing link is between the customer service and being a successful business. For the conclusion to follow logically we must assume that if a railroad is a successful business, it serves its customers well. Combined with premise (1), this assumption will make the conclusion follow logically: RR successful -> good service -> concentrate on one market, which is equivalent to: RR successful -> concentrate on one market. Let me know if this makes sense and if you have any further questions.

@irina so then isn't B correct? They want to be a successful business

@dianalazar, B is not necessary for the argument because it's not necessary that being a successful business is their first priority. Their first priority could be the health of their workers or something else instead.

So B is incorrect because of the conditional "IF" and what follows "if" is only sufficient, not necessary which means it doesn't necessarily have to be the main priority?

I think the reason b is incorrect is that is isn't critical to the argument, the argument can be true regardless of whether B is true. It is eminently reasonable that the first priority of a railroad is to serve its passengers or country, and being successful as a business is a secondary concern (this i believe is true of amtrack which is both a business and a utility). Whether or not this is true, the authors argument stands: she is not saying a railroad should strive only to be a successful business but rather she is describing the elements needed for a railroad to be a successful business.