the only one 做先行词指人,关系代词用什么?

题目

the only one 做先行词指人,关系代词用什么?
我知道the only修饰先行词时只用关系代词that
可是you are the only one of the sthdents (who) is faild the exam
先行词是the only one,也有the only修饰

答案

这个句子的确不对,应该是：
You are the only one of the students who failed the exam.
fail是不及物动词,没有在前面加上be动词Is用在被动语态中的用法.
此种情况下一般用who,不用that.
至于为什么,建议楼主不必祥究,因为大考不会死考此类无厘头的语法.