1. They are working at the scientific problems at present.
They aren't working at the scientific problems at present.
Are they working at the scientific problems at present?
2.He was waiting for you yesterday at 3 o’clock.
He wasn't waiting for you yesterday at 3 o’clock.
Was he waiting for you yesterday at 3 o’clock?
3. She is translating a german article now.
She isn't translating a german article now.
Is she translating a german article now?
4.They were listening to the lecture yesterday at 6 o’clock.
They weren't listening to the lecture yesterday at 6 o’clock.
Were they listening to the lecture yesterday at 6 o’clock?
5.He will be preparing for the exam tomorrow all day long.
He won't be preparing for the exam tomorrow all day long.
Will he be preparing for the exam tomorrow all day long?
They aren’t working at the scientific problems at present.
Are they working at the scientific problems at present?
He wasn’t waiting for you yesterday at 3 o’clock.
Was he waiting for you yesterday at 3 o’clock?
She isn’t translating a German article now.
Is she translating a German article now?
They weren’t listening to the lecture yesterday at 6 o’clock.
Were they listening to the lecture yesterday at 6 o’clock?
He won’t be preparing for the exam tomorrow all day long.
Will he be preparing for the exam tomorrow all day long?