英語語法第八講情態(tài)動詞.ppt

語法專題復習,第八講 情態(tài)動詞,1can (could)，be able to can只有現在式和過去式could兩種形式， be able to可用于現在式、過去式、將來時、完成時。要表示“能夠做某事”，可用can或be able to，但若要說過去的確運用了某種能力做成了某件事情，就只能用was/were able to，表將來具備的能力只能用will/shall be able to. (1)If you study hard，you will be able to express freely in English in three months. (2) The fire spread through the hotel very quickly but everyone was able to get out.,2could是can的過去式，但是在很多情況下，特別是在口語中，它表示語氣的委婉。因此，用could提問時，不能用could回答，而要用can或may。would、 might用于疑問句時也表委婉語氣，回答時應該用will，may。 (1)Could I borrow your dictionary? Yes，of course you can. (2)Could I call you by the first name? Yes，you may. (3)Would you be so kind as to explain the word ? Yes，I will. What is it?,3may/might，can/could都可表可能，但may/might 不能用于問句，can/could用于否定句、疑問句、感嘆句，表示驚異、懷疑，一般不用于肯定句。如果用于肯定句，則表示偶爾發(fā)生某事的可能，或某人某物一時的特點。 (1)Are you coming to Jeffs party? Im not sure. I might go to the concert instead. (2)Where can Mr. Li be? Sorry，I dont know. You can go to ask Mr. Zhang. He may help you.,(3)Mr.Bush is on time for everything. How can it be that he was late for the opening ceremony? (4)We enjoy good weather in January，but sometimes it can be terribly cold. (有時偶爾也會很冷),4must表推測用于肯定句，其否定式要用cant. 對現在表示推測：must do，cant do 對正在進行的動作表示推測：must be doing，cant be doing 對過去表示推測：must have done，cant /couldnt have done .,(1)There were already five people in the car，but they managed to take me as well. It couldnt have been a comfortable journey. (2)Jack cant have arrived yet，otherwise he would have telephoned me. (3)Put on more clothes，you must be feeling cold with only a shirt on. (4)I didnt hear the phone. I must have been asleep,5情態(tài)動詞完成體的意義 can/could have done 過去可能做過，過去本來可以做某事但沒有做 must have done 過去一定做過 may have done 可能已經做過，本來可以做但沒做 might have done 過去可能做過，過去本來可以做但沒做 cant /couldnt have done 過去不可能做過某事 should (not) have done 過去本該(不該)做，但卻沒做(做了) ought (not) to have done 過去本該(不該)做，但卻沒做(做了) neednt have done 過去本來沒必要做，但卻做了 would rather (not) have done 寧愿過去做了(沒做),注意：must have done，may have done，might have done，cant have done都表推測。其區(qū)別在于可能性的大小。must have done表很有可能，may have done表有可能，might have done表可能性很小，cant have done則為“不可能”。 (1)I told Sally how to get here，but perhaps I should have written it out for her. (2)Sorry，Im late. I might have turned off the alarm clock and gone back to sleep again.,(3)I was really anxious about you. You shouldnt have left home without a word. (4)Tom neednt have got up that early since it was Sunday and he had nothing important to do. (5)I would rather not have blamed him because he was a child after all. 6關于should的主要用法 (1)Its already seven oclock. Jack should be here at any moment. (should表推測，意為“隨時都會來”、“真該來了”。),(2)When can I come for the photos？I need them tomorrow afternoon. They should be ready by 1200.(should應該) (3)You cant imagine that a well-behaved gentleman should be so rude to a lady. (should表驚異，意為“居然”，“竟然”) (4)If he should fail to come，ask Mr. Zhang to attend the ceremony instead. (should表語氣較強的假設，意為“萬一”) (5)We should have studied last night，but we went to the concert instead. (should本應該),7關于shall的用法 shall用于第一人稱、第三人稱疑問句中，表示說話人征求對方意見或向對方請示。 shall用于第二、第三人稱，表示說話人給對方的命令、警告、允諾或威脅。 (1)Shall I go on reading the text? 我要繼續(xù)讀課文嗎？(shall征求意見) (2)Y