M4U2 grammar

He can’t have finished the work so soon.这项 工作他不可能完成得这样快。 Jack doesn't work hard at all. He can't have passed this English examination. 杰克学习根 本不用功。他不可能通过这次英语考试。
They shouldn't have left so soon.
He shouldn't have said such a thing .
2. would have done 它表示的是与过去事实相反之假设的结果， 意思是“当时就会…了” 而实际上没有… I would have helped you if I had known of your difficulties . 要是我当时知道你们的窘境 ，我就会帮助你了（而实际上没有帮助你） If it hadn't rained yesterday, we would have gone on excursion. 假如昨天没下雨，我们就 去远足了。（实际上没有去）。
1.Jack must have arrived here yesterday, _______ didn’t he? wasn’t he? 2.He must have been a policeman, _______ isn’t he? 3.He must be there now, _______ 4.You must be joking, _______ aren’t you? isn’t he? 5.He must be ill, _______
(3) shall用于条约，规定，规章等文件中，表 示一种义务，多用于第三人称中。 “The interest ___be divided into five parts, according to the agreement made by both sides.” declared the judge.
could 则表示有能力做，不侧重结果
With the help of firefighters, people in the hotel _______ escape from the burning building.
2. shall & will/ would & should shall (1)shall 用于第一、三人称的疑问句，表示征 求对方的意见 Shall I pick you up tomorrow? Shall he ring you back? (2) shall 用于第二、三人称，表示说话人的 命令、警告、允诺、威胁等 You shall do as I tell you. Don’t worry. You shall have the ticket today. He shall be punished for his being late.
Where is my pen? I must have lost it . 我的钢笔在哪？我肯定把它弄去了。
4. can’t have done 表示“过去不可能做…” She can't have gone to school, for we have no school today. 她不可能到学校去 , 今天我们学 校放假。
3. must have done
它表示“一定做过了…” 是一种对过去发生的事进 行推测。如，
No one answers the phone call, they must have already gone out . 没人接电话，他们一 定已经出去了。 They must have arrived by now. 现在他们想 必已经到达。 You must have known what he wanted . 你当时一定知道他要什么。
(2) 二者都表示请求、建议等(would更委婉) Would you please let me have a look at the book? (3) will/ would 表示习惯性,would表“过去常常” Fishes will die without water. The door won’t open. He would come to help us when he was free.
Can you have left the watch at home?你会不 会把表丢在家里呢？
6. could have done 它表示“过去本来能够…” 。
实际上没能做…
I could have run 100 metres in 12 seconds. (实 际上没能) If you had finished the task in time, you could have been promoted. （实际上没有被提升） I could have laughed to hear him talk like that.
五、情态动词+have+done”的使用情形分析
1.should (not) have done/ should not have done
“本(不)应该…(而实际上并没有…)” We should have studied last night, but we went to the concert instead. If he had joined us, we should have had a more enjoyable time.
dare (1)作实义动词 I dare to jump down from the top of the wall. She doesn’t dare (to) meet her teacher’s eyes. (2)作情态动词 --Dare you catch the mouse? --I daren’t do that. How dare you say that to your teacher? She said that she dared not walk alone at night.
A. may
B. should
C. must
D. shall
will/ would (1)二者都可表示意志或意愿(would表过去) Will you go hiking with me in the mountains? will/ would not 表示“不肯，不乐意”
No matter what I said,ቤተ መጻሕፍቲ ባይዱhe wouldn’t listen to me.
四、must表示推测：“一定，肯定” 反意疑问 句部分与must后面的动词呼应（根据陈述部 分的谓语动词或其助动词来定） He must be a visitor, isn’t he? You must have seen him at his birthday party yesterday, didn’t you? She must have finished her work, hasn’t she?
need (3) needn’t do = don’t have to 不必做 needn’t have done 本不必做…(事实上已经做了) You needn’t carry the desk out of the classroom when you clean the classroom. You needn’t have bought such a big TV as it takes too much space.
(4) 比较can 和 be able to
a.can—could而be able to 可有各种时态形式 (书P.30 1-3) b.二者都可表示“能力”, 在一般现在时里可互
换
My brother can/ is able to play football well. c. was/ were able to 表示“设法做成某事” =managed to do= succeeded in doing
should (1)出于职责、义务，“应该”= ought to You should give a phone call to your family when you go for a trip. (2) 对于某种情况的估计、推测 She shouldn’t be out in such an early morning. (3) 表示惊讶、失望的情绪，“竟然” You should be fooled by such a little child. It seems unfair that this should happen to me.
5. can (could)…have done 这种形式只用于疑问句，表示 " 含疑问语气 的推测" Where can (could) they have gone?他们能到 哪里去了呢？ How could he have forgotten such an important thing? 这么重要的事他怎么能忘了 呢？
make requests 提出要求
make suggestions 给出建议
make offers 提供帮助
give advice
提出忠告
三、比较
1 can & be able to
2 shall & will/ would & should
3 mustn’t & needn’t
4 need & dare
Modal verbs 情态动词
情态动词具有一定意义，表示说话人的语气 和态度。
情态动词没有人称和数的变化，不单独作谓 语，后面常跟动词原形。
一、情态动词可以用来谈论：
ability 能力
obligation 职责，责任
certainty 确定
permission 许可
二、情态动词还可以用来：
(3) can 表示“可能”，用于肯定句、疑问句
can’t表示否定推测 (其肯定形式是must)
Even experienced person can make mistakes.
“Whose pen can it be?” he wondered.
I saw him go out just now. He can’t be at home now.
4. need/ dare need (1)作实义动词,“需要,必要”+ n./ doing/ to do I need a dictionary, so I need to go to the book store. The car needs repairing/ to be repaired. You don’t need to tell me the complete thing. don’t have to (2)作情态动词+ do You needn’t tell me the complete thing. Need you go so early?
3. mustn’t & needn’t (1)must 表示义务或职责，“应该，必须”， 一般用于肯定句和疑问句；mustn’t 表示 “不准，禁止，不许” Everybody must obey the rules. You mustn’t lend it to others. (2) needn’t = don’t have to “不必” You needn’t watch the game if you don’t want to. (3)--Must I be home before 8 o’ clock? --Yes, you must. --No, you needn’t / don’t have to.
1. can & be able to
(1)can 表示能力，“能，能够”
The child can speak English fluently. No one can answer such a question as he asked. (2) can 表示允许，许可 You can keep the book for two weeks. You can’t smoke in this office.