Only after__ for three hours in the train hours in the rain did the reach the destination.

题目

Only after__ for three hours in the train hours in the rain did the reach the destination.
A.they had walked B.had they walked C.they walk D.do they walk

答案

选A.
Only after they had walked for three hours in the train hours in the rain did they reach the destination.
后面部分是倒装,前面部分不用倒装；后面部分是一般过去时,且有for three hours这段时间的延续,说明前面部分应该是过去完成时.因此只有A选项符合语法以及语义.