否定：Those aren't books.
These aren't pens.
He isn't a boy.
I am not a girl.
一般疑问：Are those books?Are these pens?Is he a boy?Am I a girl?肯定回答：Yes,they are.Yes,they are.Yes,he is.Yes,I am.
否定回答：NO,they aren't.NO,they aren't.No,he isn't.No,I am not.