John has been writing an essay for 6 hours.
I have been waiting here for 20 minutes.
We have been preparing for the exam since morning.
Kate has been playing the piano since 9 a.m.
She has been using my car again.
John hasn't been writing an essay for 6 hours.
I haven't been waiting here for 20 minutes.
We haven't been preparing for the exam since morning.
Kate hasn't been playing the piano since 9 a.m.
She hasn't been using my car again.
Has John been writing an essay for 6 hours?
Have I been waiting here for 20 minutes?
Have we been preparing for the exam since morning?
Has Kate been playing the piano since 9 a.m?
Has she been using my car again?