of which只能指物，有时whose可以与of whom和of which互换使用。定语从句的主语是few, little, some, most, 等时，一般只用of whom和of which。定语从句的主语是数词、形容词的最高级时，一般只用of whom和of which。

They produced two reports, neither of which contained any useful suggestions.

他们提交了两个报告，都没有任何有用的建议。

The cell is the unit of which all living organisms are composed.

细胞是构成一切生物的单位。

The trip was magical; the stuff of which dreams are made.

那是一次奇妙的旅行，宛如梦境。