非限制性定语从句中的who和whom

题目

非限制性定语从句中的who和whom
有两个句子
1.I have seen many foreigners,most of whom are from USA.
2.In our class,there are fifty students,the youngest of whom is Tom.
当中为什么用whom,不用who
这两个句子的从句中,关系代词做主语,不是用who吗

答案

因为前面有 of 做介词的宾语,既然是宾语 那就要用宾格了.of whom 来修饰前面的名词了