In recent years, railroads have been combining with each other, merging into supersystems, causing heightened concerns about monopoly. As recently as 1995, the top four railroads accounted for under 70 percent of the total ton-miles moved by rails. Next year, after a series of mergers is completed, just four railroads will control well over 90 percent of all the freight moved by major rail carriers.
Supporters of the new super systems argue that these mergers will allow for substantial cost reductions and better coordinated service. Any threat of monopoly, they argue, is removed by fierce competition from trucks. But many shippers complain that for heavy bulk commodities traveling long distances, such as coal, chemicals, and grain, trucking is too costly and the railroads therefore have them by the throat.
51. According to those who support mergers, railway monopoly is unlikely because ________.
[A] cost reduction is based on competition
[B] services call for cross-trade coordination
[C] outside competitors will continue to exist
[D] shippers will have the railway by the throat
Allow for 顾及；考虑到；带来
But many shippers complain that for heavy bulk commodities traveling long distances, such as coal, chemicals, and grain, trucking is too costly and the railroads therefore have them by the throat.
分析：句子主干是many shippers complain that ...。后面都是宾语从句的内容，该从句由therefore连接的两个分句构成，其中第一个分句是trucking is too costly，第二个分句是the railroads have them by the throat；在第一个分句前是for引导的介词短语引起话题。
本题为细节题。回答本题的关键在于识别文章提到的支持兼并的那些人持有的观点。根据文章第二段第一句Supporters of the new super systems argue that可以得知第二句话“Any threat of monopoly，they argue，is removed by fierce competition from trucks”为支持兼并的人的观点，即他们认为，垄断不可能形成是因为有公路运输的激烈竞争。因此C选项“外部竞争者将继续存在”是正确选项。