一般现在时：He is my teacher.(陈述句)
Is he your teacher?（一般疑问句）
Yes,he is.(肯定回答)
No,he isn't.（否定回答）
一般过去式： I watched TV last night.
Did you watch TV last night?
Yes,I did. No,I didn't.
现在进行时：My mother is cooking dinner.
Is your mother cooking dinner?
Yes,she is.No,she isn't.
一般将来时： I'm going to the bookstore this afternoon.
Are you going to the bookstore this afternoon?
Yes,I am.No,I'm not.