题目内容：

He walked slowly to the door___he____the reading-room.
A through came B through which could enter
C at which entered D which could enter

优质解答

b
走过门是walk through the door ,不是walk the door.
楼上的,这里的through which he could enter the reading room整个是一个从句,和前面那个to没关系
through 放前面是倒装
该句意思是 他缓慢走向那个门,那个穿过之后就能进入书房的门.
对照这个意思再分析一下原文的句子结构看我说的有没有道理.