定语从句能What引导吗?

首先可以肯定what绝对不能引导定语从句
此句是"what"引导的宾语从句,作"do"的宾语
定语从句前面一定要有可修饰的先行词(名词/代词),此句如要改成定语从句如下:
I want to do something that I want to do .
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