He began class until 2 p.m.
He did not/didn't begin class until 2 p.m.
The car went very fast.
The car did not go very fast.
The water (be) cold.
The water was not/wasn't cold.
She drank much beer.
She did not/didn't drink much beer.
I (be) a doctor last year.
I was not/wasn't a doctor last year.
They (be) ill.
They were not/weren't ill.