2003年英语阅读第三篇原文中说:Railroadstypicallychargesuch"captive"shippers20to30.Railroadstypicallychargesuch"captive"shippers20to30percentmorethantheydowhenanotherrailroadiscompetingforthebuiness.我想问

Question

2003年英语阅读第三篇原文中说:Railroads typically charge such "captive" shippers 20 to 30 .
Railroads typically charge such "captive" shippers 20 to 30 percent more than they do when another railroad is competing for the buiness.我想问一下when到底修饰 they do,还是前面一句啊.为什么

Answer 1

when引导的从句修饰they do,作they do 的状语.与平常有其它火车争业务的时候的收费相比,铁路部门一般会对这些没有其它火车可选择的托运人多收20%-30%的费用.