_______he saw in his office the day before yesterday is still a puzzle.

问题描述:

_______he saw in his office the day before yesterday is still a puzzle.
A That
B Whose
C Which
D Whom

选 D 这里的关系代词在句子中做的宾语成分 并且题目是对人提问 所以用 whom
可以这样来理解更简单 he saw sb in his office sb 所在的位置就是 whom 所在的位置 他做的事宾语