is from和come from有什么区别

虽然两句话最终意思都一样,但部分单词充当语句成份不一样.
就像:
I'm from china
I comes from china.
Where is he from和 Where does he come from
第一句Where is he from?from跟在be 动词 is 之后作表语.而he 是 第三人称单数,故be 动词用 is.也就是说is 在这里是做系动词.而不可能用 are .
而 Where does he come from?中,come from 构成一个动词短语.而主语he 是第三人称单数,可又出现在疑问句中,does 充当 come from 的助动词,故用 does.