I want to know what he said 为什么what 不可以换成that

I want to know what he said 为什么what 不可以换成that 英语句子纠错!Neither I do want to know what he said,nor do I care 为什么He'll do what he can to study hard.这句话中What 不可以改成that I want to know .What colour does he like? That is just what I want to know.可不可以写成That is what I just w What do he want to know?改错 what do they think of him?i want to know that(同义转换) i want t Can it be said I do not know what to do,just want you happy, That is just what I want to know.可以把what去掉吗/ I Know What You Want to Say i want to know what love is You know what I want to say ?