助动词do、 does.did 后面要跟动词原形,情态动词,be动词也可以提前什么时候be动词提前？什么时候助动词提前？有什么就什么提前。有助动词，动词还要提前吗？有什么就什么提前。这个与改疑问句一样的。如he teaches Chinese,疑问句does he teach Chinese?He is a Chinese.疑问句是 Is he a chinese?you may come late.疑问句May i come late?