1. Did they have their breakfast at the university dining-room?
They didn't have their breakfast at the university dining-room.
2. Did he do the translation without any difficulty?
He didn't do the translation without any difficulty.
3. Did you ski in the country yesterday?
I didn't ski in the country yesterday.
4. Did Agatha Christie write a lot of detective stories?
She didn't write a lot of detective stories.
5. Did my father buy a new adventure story yesterday?
My father didn't buy a new adventure story yesterday.