[D59] The train _______ she is traveling is arriving.

翻译：她旅行所乘坐的火车要到了.
此题考查定语从句.
1.主句为：The train is arriving.
而___ she is travelling为定语从句,修饰主句主语即先行词the train.
将先行词the train代入定语从句,变为：
(in which) she is travelling
= she is travelling (in which)
= she is travelling (in the train)
2.CD中的that/which只能直接代替先行词the train,但是the train不能直接放在she is travelling中做成分,必须加上介词才行；
by which = by the train是错误的短语,只能说by train.
如果是指具体的某辆火车the train时,介词不能用by,由此排除A.