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1、新课标高一 英语必修3,Unit 2,Healthy eating,Grammar,should 和ought to,1. should和ought to表示责任、建议或劝告，翻译为“应该”，后者语气强一些，可用于各种人称。,You should listen to the doctors advice if you want to recover soon.,Such things ought not to be allowed.,2. should接动词的完成式，是一种谴责，表示过去应该做而没有做或过去做了而不应该做。,I missed the class. I should have c
2、ome earlier.,I shouldnt have made such a foolish mistake.,3. 表示要求，命令时，语气由 should（应该）、had better最好）、must（必须）渐强。,have to和must,1. 两词都是“必须”的意思，have to 表示客观的需要, must 表示说话人主观上的看法，既主观上的必要。,My brother was very ill, so I had to call the doctor in the middle of the night. (客观上需要做这件事),He said that they must wo
3、rk hard.（主观上要做这件事）,2. have to有人称、数、时态的变化，而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。,He had to look after his sister yesterday.,3. 在否定结构中： dont have to 表示“不必”; mustnt 表示“禁止”,You dont have to tell him about it.,You mustnt tell him about it.,need和have to,1. need表示需要，主要用于否定句和疑问句。用于疑问句，肯定回答用must，否定回答用neednt h
4、ave to表示他人或客观情况要求“必须“，也可以翻译为“不得不“，have to否定形式意思是“不一定“或“没有必要“。,You neednt come if you dont want to.,I dont think you need be so polite to her.,You dont have to work so hard if you just want to pass Band 4.,Because of the heavy rain, the children have had to get up earlier than usual this week.,2. nee
5、d后面接动词的完成式，主要用于否定句，表示本可不必做某事。,“neednt +不定式完成式”表示“本来不必做，但实际做了”。,didnt need to do表示： 过去不必做某事, 事实上也没做。,Neednt have done表示： 过去不必做某事, 但事实上做了。,注：,John went to the station with the car to meet Mary, so she neednt have walked back home. There was plenty of time. She _. mustnt have hurried B. couldnt have hurried C. must not hurry D. neednt have hurried,neednt have done. 意为“本不必”，即已经做了某事，而时实际上不必要。 Mustnt have done 用法不正确，对过去发生的事情进行否定性推断应为couldnt have done, “不可能已经”。 must not do 不可以（用于一般现在时）。,
