travel by：搭乘 如:to travel by plane：乘飞机出行 后面接交通工具,表示出行方式.并且是强调方式.travel in并不是强调"旅行"而是强调经商.travel in旅行推销(某产品),四出兜销：She travels in stationery.她到处...Kate Middleton will make her first journey as a member of the Royal family in the same carriage that Diana, Princess of Wales, travelled in on her wedding day. 这句话的travel in呢作者的用意也应该是在表达一种"推销"; 这个词用得很巧,应该是把Diana的这种行为,当成了向她的臣民推销自己.这本来也是她旅行的目的.