问一道PRINCETONREVIEW上的语法题

The first political passages on modern railroad cars were a president, a senate and a governor that had been traveling to Washington, D.C. together on the Liberty Express in 1907

B.The first political passages on modern railroad cars were  a president, a senate and a governor, who traveled

C.a president, a senate and a governor were the first political passages on modern railroad cars who traveled

我选的C,答案是B,感觉C要顺一些,P上的解释说C错因为WHO TRAVELED TO ...修饰CARS 但是WHO只是修饰人而已,所以是跳跃修饰吧.