Katia will introduce me to some of her friends,one of whom has been to China several times.
问题描述：
Katia will introduce me to some of her friends,one of whom has been to China several times.
这里引导定语从句的关系代词为社么不用WHO呢?不是在从句中作主语吗?
答
of whom介宾优先.one of whom整个词才是在句中作主语.