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.http://yingyu.chazidian.com （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引导定语从句时 ，通常用作关系代词，而引导名词性从句时，是个不充当任何成分的连接词。宾语从句和表语从句中的that常可省略。What只能引导名词性从 句， 用作连接代词，作从句的具体成分，且不能省略。 I think (that) you will like the stamps. What we need is more practice.