看句中的
谓语动词, 有is,就用is提问。谓语动词是原形, 用do。谓语动词是三单,加s,就用does。谓语动词是过去式ed, 就用did
He is 14. He isn't 14.
He is playing basketball. He isn't playing basketball.
He plays bastetball well. He doesn't play basketball well.
They go to school on foot. They don't go to school on foot.
I washed my clothes yesterday. Ididn't wash my clothes yesterday.
注意:用了does和did之后,原来的动词用原形