have用于第一第二人称（i ,you),has用语第三人称he/she
was/were是is/are的过去时.放主语后面 做谓语
should/would 后跟动词原形 should是应该是意思.语法should have done(done意思是动词过去分词）意思是本应该做什么,实际是却没做,WOULD ,一般用法,WOULD LIKE TO do sth,意思是更愿意做某事
did是DO的过去时,does是DO的复数形式,
do和does是一般现在时的助动词,did是一般过去时的助动词,does
用于第三人称,而do是第一人称,用于疑问句
eg,How do you know the answer?
How does she know the answer?
Where did he go yesterday?