We shouldn't spend our money testing so many people,most of

We shouldn't spend our money testing so many people,most of __ are healty. 为什么用whom不用 who,详
请快一点帮我回答，赶时间，谢谢！ 此为非限制性定语从句，关系词的使用要以先行词在从句中所担任的句子成分而定，而Most people are healty,people不做主语吗？