do的用法:1.做实义动词,有单三形式does,可以在句子中做谓语.
eg.I often do my homework.He often does his homework.(做作业)
2.做助动词.同样有单三形式does,但是本身没有实在意义,只是用在否定句和一般疑问句中,与谓语动词一起构成否定和疑问结构.在变否定句和一般疑问句时,如果是实义动词(即不是be动词和情态动词)做谓语,则需要根据主语人称形式借助它们.
eg: He plays football---He doesn't play football
---Does he play footba
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