全国大众英语测验语法——what/whatever;that/what;who/whoever
1）what = the thing which；whatever = anything
What you want has been sent here.
Whatever you want makes no difference to me.
2) who= the person that whoever= anyone who
（错）Who breaks the law will be punished.
（错）Whoever robbed the bank is not clear.
（对）Whoever breaks the law will be punished.
（对）Who robbed the bank is not clear.
3) that和 what
当that指导定语从句时，每每用作干系代词，而指导名词性从句时，是个不充当任何身分的连接词。宾语从句和表语从句中的that常可省略。What只能指导名词性从句，用作连接代词，作从句的详细身分，且不能省略。
I think (that) you will like the stamps.
What we need is more practice.