Question

定语从句这里为什么用who, 不用that？

If she could make it, she would be the first person in the world who did it.
定语从句中，先行词有first等序数词修饰，要用that作引导词。但正确答案是who，请英语老师帮忙解释一下，谢谢！

Answer 1

先行词有序数词修饰时只能用that 不用which. 但是修饰的是人时用who

Answer 2

我也认为用who是错的，先行词前有序数词修饰时引导词一定是用that

又如
He was the first student that finished the
homework他是第一个完成作业的学生

追问

刚才我查了资料，因为先行词和定语从句被状语in the world隔开了,所以必须使用who，而不能用that。这句话是山西省2018年中考选词填空的原题。