1.WE were in zhe playground yesterday.
We were not in the playground yesterday.
Were you in the playground yesterday?
Yes,we were./ No,we weren't.
2.I went to the park last Sunday.
I didn't go to the park last Sunday.
Did you go to the park last Sunday?
Yes,we did./No,we didn't.
3.They bought a car two days ago.
They didn't buy a car two days ago.
Did they buy a car two days ago?
Yes,they did ./ No,they didn't.