3、must的基本用法
(1)must表示"必须"、"应该"之意,其否定式 must not,缩写形式为 mustn't,表示"不应该","不准"、"不许可"或"禁止"之意,如:We must study hard and make progress every day. You mustn't touch the fire. (2)对以must提出的疑问句,如作否定回答时,要用needn't或用don't (doesn't) have to (不 必)来回答,而不用mustn't,因为mustn't表示的是"禁止"或"不许可"之意,如:---- Must we finish the work tomorrow? ---- No, you needn't (don't have to), but you must finish it in three days. (3)在肯定句中must可以表示推测,表示"一定"或"必定"之意,如:---- Whose new bike can it be? ---- It must be Liu Dong's. I know his father has just bought him a new one.
4、can, could, may, must后接完成式的用法
(1)can, could后接完成式的用法:①在否定句或疑问句中表示对过去发生过的事情的"怀疑"或"不肯定"的态度,Could he have said so? ②在肯定句中,可以表示过去可能做到而实际并没做到的事情,有"劝告"或"责备"的语气。如:---- When did you answer her letter? ---- Only yesterday. ---- It's too late. You could have answered it earlier, I am sure. (2)may, might后接完成式的用法 ①表示对过去某事的推测,认为某一件事情在过去可能发生了。如果使用might,语气就比较婉转或更加不肯定,如:Mary might have learned some Chinese before. ②可以表示过去本来可以做到而实 际没有做到的事情,有"劝告"或"责备"的语气,如:You didn't do the work well that day. You might have done it better. (3)must后接完成式的用法:表示对过去某事的推测,认为某事在过去一定做到 了,如:Liu Dong isn't in the classroom. He must have gone to the library.
【语法复习十一:助动词与情态动词】相关文章:
最新
2016-11-24
2016-11-24
2016-11-09
2016-11-04
2016-11-04
2016-11-02