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助动词是?怎么用

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助动词是?怎么用
助动词是?怎么用
助动词是协助主要动词构成谓语动词词组的词,分为基本助动词,情态动词,半助动词.
1.基本助动词只有三个:be .do .have
它们没有意义,只起语法作用,和表示语法意义.
be
I am listening to a Beethoven symhony.
do
I do think you'll have a hard job.
have
Joan has seen that movie.
2.情态助动词有13个
can /could/ may /might/ will/ would/ shall /should/ must/ ought to/dare/need/used to
它们表示情态意义,
它们后面的主动词是不带to的动词原形.
It may snow before nightfall.
(其它都一样)
3.半助动词有have to/seem to 之类的结构,它们也是表示情态意义.
I have to buy a new car.