Нужно три предложения в past perfect continuous : утвердительное, вопросительное, отрицательное. но только чтобы они не были разными , а одного содержания: изменить одно предложение(утвердительное) в вопросительное и отрицательное.
He has been doing his homework since early morning. He hasn't been doing his homework since early morning. Has he been doing his homework since early morning?
He hasn't been doing his homework since early morning.
Has he been doing his homework since early morning?