情态动词must的用法

一、must的含义1.1.表示义务、意图或建议表示义务、意图或建议:必须必须 You must do your homework first.I must get up early.2.2.表示推测表示推测:一定一定,必定必定 He must be at home.The pen must be Jims.二、must的用法：1 1、肯定式：、肯定式：must+V原；原；You must finish your homework.2、否定式：否定式：must+not+V原；原；You mustnt smoke here.must not表示禁止表示禁止3 3、疑问式：、疑问式：Must+Must+主语主语?Must I clean the room at once?我必须马上打我必须马上打 扫房吗？扫房吗？Yes,you must.是的，你必须马上打扫。是的，你必须马上打扫。No,you dont have to(=neednt).不必啦。不必啦。在回答在回答must引起的问句时，如果是否定的答引起的问句时，如果是否定的答复，可用复，可用dont have to或或neednt(不必不必)，但不能用但不能用mustnt t三、must 与have to 的区别别1 1、must must 强调主观上认为强调主观上认为“必须必须”做某事做某事,而而 have to have to 强调客观上要求强调客观上要求“不得不不得不”做某事。做某事。I have to look after my sister.For my mother went out.I must work hard.客观需要客观需要主观意愿主观意愿I had to clean my bedroom yesterday.He has to work hard.He doesnt have to work hard.-Does he have to work hard?-Yes,he does./No,he doesnt.2 2、在肯定句中，、在肯定句中，have to 随人称和时态的不随人称和时态的不同而变化。其否定式和疑问式同而变化。其否定式和疑问式 的构成与行的构成与行为动词为动词havehave相同，需使用助动词。相同，需使用助动词。请用请用must或或have to的适当形式填空的适当形式填空1.We _ be polite to our teachers at school.2.You _ go outside to play as it is snowing heavily.3.Must I get to the station before 5 p.m.?Yes,you _./No,you _.4.I got up late this morning,so I _ take a taxi to school.5.Does she _ stay at home?No,she doesnt.mustntmusthad tohave tomustdont have to/neednt