who that 与that who 的区别

题目

who that 与that who 的区别
---------- knows the truth about it will tell you.
A who that B that C whoever D That who .
.
为什么是C?不是D?
who that 与 that who有什么区别?
我就知道A不能选.因为句尾不是问号.

答案

Whoever knows the truth about it will tell you.
不管是谁知道了真相,他会告诉你.
原句等于:Whoever(that knows the truth about it )will tell you.
就是说,原句已经有that 了,而且里面有一个定语从句.
如果用D
就成了：
That who that knows.
明显是不通的.