定语从句的题求高人给讲解下!In our factory there are 2,000 workers,two thirds of ____ are women

定语从句的题求高人给讲解下!In our factory there are 2,000 workers,two thirds of ____ are women
In our factory there are 2,000 workers,two thirds of ____ are women.A.them B.which C.whom D.who
选D不行吗?这个句子“two thirds of ____ ” 中的空的这部分的句子成分是什么啊?
再比如.one of us 中为什么要用us