Sam plays basketball.(做否定回答）
答案：--Is Sam playing basketball?
----No,he isn't.
My brother writes an e—mail.（做肯定回答)
答案：----Is your brother writing an e-mail?
-----Yes,he is.
My parents pick up apples.(做否定回答）
答案：----Are your parents picking up apples?
-----No,they aren't.
The kids count ants.（做肯定回答)
答案：----Are the kids counting ants?
------Yes,they are.