tom has finished his homework doesn't he

问题描述:

tom has finished his homework doesn't he
Tom has finished his work,_____he?
为什么用 hasn't
什么时候用doesn't
?讲解仔细点
例题

因为前面是现在完成时态,有助动词HAS,故要用hasn‘t,不能用doesn't.
比较:Tom finishes his work,doesn't he?