He can dance very well,can`t he? Разделительный
Сan he dance very well? Общий
Who can dance very well? Вопрос к подлежащему
What can he do very well? Специальный
Can he dance or sing very well? Альтернативный
They must help their grandparents,mustn`t they? Разделительный
Must they help their grandparents?Общий
Who must help their grandparents? Вопрос к подлежащему
Must they help their grandparents or parents? Альтернативный
What must they do? Специальный