请问定语从句也可以修饰整句吗?那先行词就是一个句子了吗?比如这句

Helen was much kinder to her youngest child than she was to the others, which, of course, made others jealous. 这句句子非常规范,而且 wich 引出的定语从句修饰主句很清楚.
what 是名词性从句的引导词,不能在这里引导定语从句.