A business analysis of the Appenian railroad system divided its long-distance passenger routes into two categories: rural routes and interurban routes. The analysis found that, unlike the interurban routes, few rural routes carried a high enough passenger volume to be profitable. Closing unprofitable rural routes, however, will not necessarily enhance the profitability of the whole system, since__. Which of the following most logically completes the passage? ["not all of Appenia's large cities are equally well served by interurban railroad services", 'the rural routes were all originally constructed at least one hundred years ago, whereas some of the interurban routes were constructed recently for new high-speed express trains', 'a large part of the passenger volume on interurban routes is accounted for by passengers who begin or end their journeys on rural routes', "the greatest passenger volume, relative to the routes' capacity, is not on either category of long-distance routes but is on suburban commuter routes"]