that is all I want这个句子的疑问

貌似有省略，完整句子应该是 that is all that I want，还是that is all what I want，还是that is all that I want for？

Is it/that all you want? 疑问句be动词提前
一般可以说
Q: Is that all?
A: That is all I want.

解释：that i want 是定语从句修饰先行词“all” .that 代表先行词 all 在定语从句中作宾语，这儿没有省略that ,，修饰先行词是“all,”时，关系代词作主语或宾语时，只能用that,不能用which ,这是英语的语法规定。 all that i want 意思是：我想要的一切。例句：all that i gave was likely to consider as negligible . 我所给出的所有一切就是可能把 ...（事情）认为是微不足道的。 希望对你有帮助