2． Helen was much kinder to her youngest son than to the others, __________, of course, made the others envy him.
A. who B. that C. what D. which
【解析】这是一句非限制性定语从句，关系代词指代整个句子Helen was much kinder to her youngest son than to the others，且从句中行为动词made是主动语态，因此选择which。
