Have thechildren been
cleaning their room since10 o'clock? Общий
Since what time have the children been cleaning their room? специальный
Have the children been cleaning their room since 10 or 12 o'clock? альтернативный
The children have been cleaning their room since 10 o'clock, haven't they? разделительный
Who has been cleaning their room since 10
o'clock? вопрос к подлежащему