They are firefighters. They aren't policemen.
They were firefighters. They weren't policemen.
History class isn't fun. It is boring.
History class wasn't fun. It was boring.
She isn't a doctor. She's a nurse.
She wasn't a doctor. She was a nurse.
We are hot.
We were hot.
You are a student.
You were a student.
He isn't busy.
He wasn't busy.
I am late for school.
I was late for school.
I'm not hungry. I'm thirsty.
I wasn't hungry. I was thirsty.
The party is fun.
The party was fun.
You are bored.
You were bored.
They are excited.
They were excited.
She is happy.
She was happy.