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1、小议情态动词Must 和Have to 的用法区别Must 和Have to二者均有“必须”的意思，其后均用动词原形形式。但是二者用法又有明显不同，下面将做详细说明：A:关于Must 的用法：1、Must 用来表示必须时，强调的是主观需要，发自自身内心的概念。2、Must 作为情态动词而言，没有人称、单复数和动词时态的变化。3、含有情态动词must的肯定句变为一般疑问句时，需要将must提前到句首，注意第一人称和第二人称的转换形式即可。对于一般疑问句的回答，其肯定回答要用Yes,主语+must。而对于其否定回答则不能用mustnt，因为mustnt表示不准、不应该，是一个表示命令性的禁止语气的
2、单词，而此处的语气是一种劝告、劝说的语气，所以只能用neednt或者是donthave to 进行回答。如：Must I finish homework this afternoon?Yes, you must.No, you neednt. or: you dont have to .4、含有情态动词must的句子要变为否定句只需要在must后面直接添加否定词not 即可，变为mustnt，如We students mustnt play soccer in the street .B:关于情态动词have to 的用法：Have to 也表示必须，但强调的是客观需要，有不得不、被逼无奈的做
3、某事。此词既有人称、单复数的变化、也有动词时态的变化。同时其否定形式和其疑问句形式均需要借助助动词do才可以进行变化。如：We have to stay in the classroom because we didnt finishour homework.She has to look after her mother at home.Does he have to go to bed now?Yes, he does./ /No, he doesnt .We dont have to clean the clean today.I will have to finish reading
4、the novel because my deskmate wants to get it this afternoon.C: must 还有表示“肯定性”猜测的语气，意思是“一定，肯定”的概念。如：This book must be Toms because his name is on the cover of the book .The teacher must be in the office .The light is on now.She must have a camera because I often see her take photos.此时一定要注意表示“可能性”猜测语气（may）和“不可能性”猜测语气（cant）的用法。May: She may be our English Teacher.Cant: The man you saw in the street cant be Mr Smith . He has already gone to Fengqiu .至于情态动词Must 和have to 区别，若是还有未涉及到的地方，恳请各位老师批评指正。谢谢！2013.11.10