参考答案

正确答案：D
解析：态度揣摩题。关于captive shipper文中提及很多次，多次表达了他们对铁路合并的态度，如“i)many shippers complain that for heavy bulk commodities traveling long distances， trucking is too costly；ii)Shippers who feel that they are being overcharged．．．iii)Many captive shippers also worry they will soon be hit with a round of huge rate increases；iv)Many captive shippers fear that they will，as Norfolk Southern and CSX increase their grip on the market．”，总体而言，captive shippers是不满、抱怨、担忧和担心的态度，因此正确答案为D项。