Thank you! By the way, you mean that I can reply to questions using only a grammar that was used in those questions. And can't I reply by saying "I've been sleeping" to show the continuation of my action if I'm asked "What did you do" (instead of "what have you been doing")?
Native speakers will answer a question with the same verbal aspect as the question itself, because that is in the meaning of what is being asked.
Verbal aspect indicates the flow of time with respect to the action. Is the action completed? Is it still continuing? Will it continue into the future? Is it habitual? Is it repetitive?