.Mr Green often flies back home _____ an airplane,and Mrs Green often goes_____ train .
问题描述：
.Mr Green often flies back home _____ an airplane,and Mrs Green often goes_____ train .
A.in; by B.in; in C.by; by D.by,in
答
A
by 后直接加交通工具,不能加冠词.有冠词就得用in或者on,in是全封闭或半封闭的如飞机,火车等,on如自行车,摩托等.