Were they working on the computer two hours ago?
Yes, they were.
Were they watching TV?
Yes, they were.
Was she mowing the lawn?
No, she wasn't.
Was he working on the computer?
No, he wasn't.
Was he taking out the trash last Sunday?
No, he wasn't.
Was she doing the dishes yesterday morning?
Yes, she was.
Was she walking the dog yesterday?
Yes, she was.
Were they doing the laundry?
Yes, they were.
Was she walking the dog last Saturday?
No, she wasn't.
Was she talking on the phone this morning?
Yes, she was.