答案：C

题目分析：“介词 + which / whom”引导的定语从句

关系代词在定语从句中作介词的宾语时，常常将介词前置于作宾语的关系词前，

I love the music that I can dance to. =" I" love the music to which I can dance.

The man who I talked to just now is my brother.=" The" man to whom I talked just now is my brother.

介词后面的关系词指人时只用whom, 不能用who或that; 指物时只用which,不能用that.

注意，并非所有情况下介词都可以前移，含有介词的短语动词不可拆开，介词仍需放在动词后面，如：look for, look after, take care of等。

“介词+ which / whom”前还可以用some, any, none, all, both, neither, many, most, each, few等代词，名词或数词等。

His sons, both of whom loved music very much, spent most of their money on CDs.

The house, the roof of which is blue, will be used as a library.

whose的用法：

指代人或物，在从句中作定语，表示“他/它的”：We all dislike the boy whose father is a manager.

这里也可以用whose roof；whose+名词=the+名词+ of which=" of" which the名词，故选C。

点评：本题难度适中。

即学即练：He is using a desk _______ are not of the same length.

A. whose  legs  B. the legs of whose   C.  legs of which   D. which legs

解析：A 。句意：他正在用一张桌腿不一样长的桌子。