单选题 4.Which of the following most logically completes the passage?
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________.

A、 a large part of the passenger volume on interurban routes is accounted for by passengers who begin or end their journeys on rural routes
B、 within the last two decades several of the least used rural routes have been closed and their passenger services have been replaced by buses
C、 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
D、 not all of Appenia's large cities are equally well served by interurban railroad services
E、 the greatest passenger volume, relative to the routes' capacity, is not on either category of long-distance routes but is on suburban commuter routes

【正确答案】 A

【答案解析】Argument Construction
Situation In the Appenian railroad system, interurban routes generally carry enough passengers to be profitable, but few rural routes do.
Reasoning What would suggest that closing unprofitable rural routes would not enhance the railroad system's profitability? Any evidence that closing the unprofitable rural routes would indirectly reduce the profitability of other components of the railroad system would support the conclusion that closing those rural routes will not enhance the system's profitability. Thus, a statement providing such evidence would logically complete the passage.
A Correct. This suggests that closing the rural routes could discourage many passengers from traveling on the profitable interurban routes as well, thus reducing the profitability of the railroad system as a whole.
B Even if some of the least used rural routes have already been closed, it remains true that most of the remaining rural routes are too little used to be profitable.
C Closing very old routes would be at least as likely to enhance the railroad system's profitability as closing newer routes would be.
D Even if there is better railroad service to some large cities than others, closing unprofitable rural routes could still enhance the system's profitability.
E Even if suburban routes are the most heavily used and profitable, closing underused, unprofitable rural routes could still enhance the system's profitability.
The correct answer is A.