同学你好，该知识点来自沪江网校《大学水平直达雅思7分【全额奖学金班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
因为of是介词，介词后面需要宾格代词，因此只能是whom

About six thousand people were arrested, several hundred of whom have since been released.
约6,000人被捕，后来其中的几百人又被释放了。

We have two full-time secretaries, one of whom is on secondment from the Royal Navy.
我们有两个全职秘书，其中一人是临时从皇家海军调来的。

Boats crammed with hot and angry holidaymakers, some of whom had waited for up to two days to cross.
船上满是情绪激动、怒气冲冲的度假者，有些人等船渡河已经等了两天了。

祝同学学习进步~