定语从句中what在什么情况下才能用做关系代词?它和that的区别是什么?

what不能做定语从句的关系词.限制性定语从句只能用that 的几种情况1．当先行词是anything,everything,nothing (something 除外),few,all,none,little,some 等代词时,或者是由every,any,all,some,no,little,few,much ...