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1、Part II Grammar情态动词（II）思维导图(表示责任或义务表示劝告、建议或命令 座示推测ought to的用法情态动词n, 陶图精讲 ,、ought to的用法表示责任和义务，意为“应该，与should同义，但语气比should重，侧重于“责任、义 务、道德、法律”等方面。To be a popular student, we ought to be strict with ourselves.为了成为一名受欢迎的学生，我们应该对自己要求更加严格。名师点津ought to的否定形式为ought not to(oughtrft to); 一般疑问句形式是将ought提至 句首，其否定
2、答语通常用dont have to或neednt。一Ought he to see the doctor?他该去看医生吗？一Yes, heto./No to./No, he doesnt have to.是的，他该去。/不，他不必去。You ought not to make this kind of mistake again.你不应该再犯这种错误了。表示可能性，一般指较大的可能性，意为“按道理应该”。If he started at six, he ought to be here now.要是他6点就出发的话，这会儿该到这里了。二、need的用法.作情态动词(l)need作情态动词时，常
3、用于疑问句、否定句或条件句中，意为“需要二一Need I finish the work today?must./No must./No, you neednt.我需要今天干完这活吗？是的，必须干完。/不用，你不必干完。(2)needn9t意为“不必”，表示客观上不必如此。time.Youplenty of time.You neednt drive so fast.时间很充足，你不必开这么快。1 .作实义动词need作实义动词时, 后可接名词、动名词、不定式等，有人称、时态和数的变化。The bike needs repairing.=The bike needs to be repaire
4、d.这辆自行车需要修理。三、have to(l)have to表示客观上的必要性，意为“不得不”。由于它是由“have+to”构成，因此它有 多种时态变化形式以及人称和数的变化，其疑问句式和否定句式由助动词do构成。Its tlate.Ilate.I have to go home now.天色太晚了，我现在得回家了。Did you have to leave now?你现在必须得走吗？We dont have to go to school on Sundays.星期天我们用不着上学。（2川丫匕10的否定式11011*1丫0 10,表示没有义务或没有必要做某事，意为“不必”，常可以 回答以m
5、ust开头的疑问句。而must的否定式mustiTt表示“禁止，不许”。You dont have to finish the work now.你现在没有必要完成这项工作。一Must we hand in our homework this afternoon?我们必须今天下午交家庭作业吗？一No, you dont have to/you neednt不，你们不必。（肯定回答为：Yes, you must.）（3）have to表示客观需要，而must则表示主观的看法。You must obey the rules of your school.你必须遵守学校的规章制度。I have to
6、 go now because its getting dark.天快黑了，我必须得走了。四、情态动词+havedone“情态动词+havedone”表示对过去事情的推测。各情态动词的这种具体用法如下表：can/could have done1 .过去可能（表推测）2 .本能做而未做（表虚拟）should/ought to have done本该做而未做may/might have done1 .过去也许做了 （表推测）2 .本可能做而未做（表虚拟）must have done一定已经做了neednt have done本不必做而做了From what you said, she must h
7、ave told you all about it.从你所说的来看，她一定把一切都告诉你了。You should have told me earlier or I might have gone with them. 你应该早点告诉我，不然的话我就会和他们一块去了。They could have sent up the satellite successfully.他们本来可以成功发射这颗卫星的。You ought to/should have been more careful.你本应该更小心一些的。You neednt have told them about it.你本来没有必要告诉他
8、们那件事。I .选词填空l.You mustnt go there alone； its too dangerous.(mustn,t/needn)2 .The park is so beautiful, so we shouldnt throw away rubbish everywhere, (shouldnt/cant).You oughtnt to have spent so much time playing computer games, (mustif t/oughtnt to)3 .一Shall I leave the room so that you two can talk
9、?-No, you neednt.(mustnt/neednt).They ought to win fbr theyve trained hard enough.(ought to/must)4 .They had to stay in the office last night because of the snowstorm.（have to/must）.一Must I finish my work today?一No, you neednt.（need/must）.As an athlete, he has to know his strengths and weaknesses.（h
10、ave to/need）5 .He finished all the work himself； in fact, he could have asked his friends for help.（need/could） lO.Something bad must have happened if Mr.Brown didnt turn up on time to have class as he always did.（have to/must）II .补全句子1.1 have just found that I had to attend an important class meeti
11、ng （我必须参力口一个重 要的班会）that afternoon.2.George cant have gong too far（不可育自走太远）.His coffee is still warm.1.1 love the weekend, because I neednt get up early（不必早起）on Saturdays and Sundays.4 .The length of the article should be limited to 400 words or so （应当 F艮制J在 400 词左 右）.5 .The last important thing you
12、should remember （你应当记住的）is that you have to send the article to me before June 28.1.1 badly need someone to help me with my oral English （需要有人来帮助我学英 语 口 语），at which lots of Chinese students are bad.7 .You neednt have referred to it （本不必提起它），for I had known about it.8 .You must have seen （肯定看过）the film The Pursuit of Happiness.9 .Mr.Smith cant have gong to Beijing （不可能去北京 了），for I saw him in the library just now.10 .You oughtnt to/shouldnt have written （本不应该写）so fast.