She is the only person who understands me还是that understands methe only不影响关系代词的选择吗？

She is the only person who understands me还是that understands me
the only不影响关系代词的选择吗？

这是定语从句的问题,
如果先行词前有 the only,那么,关系代词肯定用that
肯定!
如果有最高级,亦如此

She is the only person who understands me
who是指前面的person
that后面跟定语从句需要跟一个完整的句子

who