2．would 和used to的用法区别。 ①used to表示过去与现在或过去某时与后来的情况有不同，强调“现已无此习惯了”，而would只表示过去的情况，与现在无关。 When he was young, he would smoke a lot. 他年轻时总是吸许多烟。（不含有和现在比较，现在他也许还在抽，也许不抽了。） He used to live in the country, but now he lives in the city. 他过去住在乡下，现在住在城里。 ②used to可表示过去的习惯动作或状态，而would只表示过去的习惯动作。 Kate used to be very thin. 以前凯特非常瘦。 There used to be a building at the street corner, but it has been pulled down. 街道拐角处过去有座楼房，现在拆了。（不用would） ③used to可泛指过去的习惯动作或状态，而would表示过去的习惯动作时，往往要带有一个特定的时间状语。 【误】We would play hide-and-seek in the fields. 【正】We used to play hide-and-seek in the fields. 我们过去常在田野里玩捉迷藏。 【正】Whenever we were in the country, we would play hide-and-seek in the fields. 每当我们在乡下，我们都在田野里玩捉迷藏。
H．dare dare既可用作情态动词，也可用作行为动词，指勇气和胆量上的可能，可译为“敢”。 1．情态动词dare ①dare作为情态动词时主要用于疑问句和否定句，一般不用于肯定句中。 I dare not daren't walk through the forest at night. 我不敢在黑夜穿过森林。 --- Dare you walk through the forest at night 你敢在黑夜穿过森林吗？ --- Yes, I dare. 是的，我敢。 --- No, I daren't. 不，我不敢。 He dare not drive too fast on the rainy day. 下雨天他不敢开得太快。 He dared not do it last year. 去年他不敢做这事。（dare的过去时为dared）
②可以用于表示怀疑的名词性从句中。 I wonder how he dare say such things. 我真奇怪他怎么竟敢说出这样的话。 We don't know whether he dare climb the mountain. 我们不知道他是否敢爬那座山。 ③可以用于条件状语从句中。 If the enemy dare enter the village, we'll fight against them to the end. 如果敌人敢进入村里，我们就和他们战斗到底。 If you dare cheat in your exam, I will give you some punishment. 如果你们敢在考试中作弊，我就惩罚你们。
2．行为动词dare ① dare可以作为行为动词，多用于肯定句中，但也可用在疑问句和否定句中 He will dare any danger. 他敢面对任何危险。 He dared me to jump over the stream. 他激我跳过小溪。 Did anyone dare to admit it 有人敢于承认吗？ I have never dared (to) go back to take a look. 我再也不敢返回去看一眼了。（否定句中to可省略） ②和其他行为动词一样，dare在句子中要随着主语的人称和数发生变化。 He doesn't dare to walk at night. 他不敢走夜路。（作行为动词） He daren't walk at night. 他不敢走夜路。（作情态动词） Does he dare to walk at night 他敢走夜路吗？（作行为动词） Dare he walk at night 他敢走夜路吗？（作情态动词） He didn't dare to walk at night fifteen years ago. 15年前他不敢走夜路。（作行为动词） He daren't walk (=dared not walk) at night fifteen years ago. 15年前他不敢走夜路。（作情态动词） Will you dare to do the same experiment tomorrow 明天你敢做同样的实验吗？（作行为动词） Dare you do the same experiment tomorrow？ 明天你敢做同样的实验吗？ （作情态动词） 必背： 英语口语中dare的几个常用结构： ● I dare say... 我想, 大概, 可能, 或许…… I dare say things will improve. 我想情况会好转的。 ● How dare you ... 你怎么敢……？ How dare you ask me such a question ? 你怎么敢问我这样的问题？ ● I dare you ... 我谅你也不敢…… I dare you to tell your parents!我谅你也不敢告诉你父母！
I．need 1．情态动词need need 和dare一样，作为情态动词时，主要用于否定句和疑问句，一般不用于肯定句中（在肯定句中常被 must, have to, ought to, should等情态动词取代）。作为情态动词，它的词形只有need一种形式。 You needn't return the book now. You can keep it till next week if you like. 你现在不必还书， 如果愿意，你可以下周还。（needn't = don't have to） Need I hand in my homework now 我现在就要交家庭作业吗？ --- Need he finish the article next week 他要下个星期完成这篇文章吗？ --- Yes, he must. 是的，他必须完成。 --- No, he needn't. 不，他不需要。（= he doesn't have to）
2．行为动词need need和dare一样，也可以作行为动词，可用于肯定句、否定句和疑问句中。行为动词need有人称和数的变化。 Plant needs water. 植物需要水。 My shirt needs a button. 我的衬衫需要一枚钮扣。 My car needs repairing. 我的车该修理了。 He has grown up. We don't need to worry about him. 他已经长大了，我们不必为他担心。 You don't need to buy so many things for the picnic. 你不必为这次野餐买这么多东西。 Patience is needed for that job. 干那工作，需要耐心。 提示： Need作为情态动态时，不要用于肯定句中。 【误】She need do her homework by herself. (need作为情态动词时，不用于肯定句中) 【正】She needs to do her homework by herself. 她该独立完成家庭作业。三、 情态动词+动词完成式
“情态动词+have done”是情态动词的一个十分重要的结构，这种结构有两个主要的用法。 表示对过去发生的动作或状态的推测或估计 may might have done 表示“大概已经” 通常用于肯定句和否定句。 might有时可用于疑问句。 can could have done 表示“可能已经” 通常用于疑问句和否定句。 could有时可用于肯定句。 must have done 表示“一定已经” 只用于肯定句，具有较大的可能性 should have done表示“该”,可能性较小 表示对过去发生的动作的遗憾或责备 might have done 表示“本可以 通常用于肯定句 could have done 表示“本可以 通常用于肯定句。 should have done 表示“应该 可用于肯定句、否定句和疑问句。 ought to have done 表示“应该” 同should have done。 needn't have done 表示“本没有必要” 只用于否定句。A． may /might /have done 1．表示对过去事实不大肯定的推测，常译为“可能已经”。 They might have taken a later train. 也许他们乘坐的是晚一点儿的火车。 He seems to know the city quite well. He may have been there before. 他似乎对那个城市很熟悉，他以前可能去过那儿。 2．表示“本来应该或可以做但没有做某事”，含有轻微的责备口吻或遗憾。 You might have given him more help, though you were busy. 你本来应该给他更多的帮助，虽然你很忙。 The proposal might have been refused. 这个建议本该拒绝的。
B． can could have done
1．表示对过去事实的推测，常用于否定句和疑问句。 He can't couldn't have watched TV yesterday for he knew they would have an exam. 昨天他不可能看电视，因为他知道快要考试了。 I don't know why she didn't call me yesterday. Can (Could) she have forgotten my telephone number 我不知道昨天她为什么没给我打电话，难道她会把我的电话号码忘了吗？ He didn't come to school yesterday. Can he have been ill 他昨天没来学校，难道他生病了？
2．could可表示对过去能做而未做的事感到惋惜、遗憾，可译成“本来是可以……的”。 Why didn't Sophie apply for the job She could have got it. 为什么索菲不申请这项工作？她本来是能得到的。 Why did you stay at a hotel when you went to New York You could have stayed with Barbara. 你到纽约时为什么住宾馆？你完全可以和芭芭拉住在一起的。 Given more time, we could have done the work better. 如果给我们更多的时间，我们完全可以把这项工作干得更好。
C． must have done
1．表示对过去事实有把握的推测，具有较大的可能性。只用于肯定句中，否定句和疑问句用can could have done。 His watch must have stopped. 他的表肯定停了。 --- I rang your flat yesterday. A man answered but I didn't recognize the voice. 昨天我给你家打电话，一位男士接了电话，但我没听出来是谁的声音。 --- Oh, it must have been my brother Peter. 哦，那一定是我哥哥彼得。
2．用于虚拟语气中时，表示与过去事实相反。 You must have caught the bus if you had got up earlier. 如果你早一点儿起床的话，你准能赶上那一班公共汽车了。（事实上没有赶上公共汽车） He must have won the game if he had been careful enough. 如果他足够细心的话，他准能赢得比赛。.
D． needn't have done 用于对过去的责备，表示“没有必要做某事，可是做了”。 The airport is close to us. You needn't have hurried there early. 机场离这儿很近，你没必要早早地赶到那里。（可是你早早地到那儿了） He is still young. You needn't have sent him such an expensive present. 他还小，你没必要送他这么昂贵的礼物。 注意： 如表示“过去不必做也没有做”之意，需用didn't need to do。 It is not cold today. I didn't need to take the thick sweaters out. 今天天气不冷，我没有必要把厚毛衣拿出来。（实际上也没拿）E． should ought to have done
1．表示对过去动作的责备或批评。 You should have gone over your lessons. (In fact you didn't go over your lessons.) 你们应把功课复习好的。（可事实上你们没有。） You shouldn't have watched TV last night. (In fact you watched TV last night.) 你们昨天晚上本不该看电视。（可你们看了。）
You oughtn't to have entered the teachers' office without permission. 没有经过允许，你们本不该进老师的办公室。 You oughtn't to have gone to the deserted place alone. 你不该独自去那荒凉之地。
2．表示期待或推测。 If the flight was on time, you should ought to have arrived in Shanghai early this morning. 如果航班准点的话，你今早就能到上海了。 The building should ought to have been completed by the end of the week. 这幢建筑物本周末前应该能完工。
F．would have done表示与过去事实相反的假设或结果。 I would have been happy to see him, but I didn't have time. 我会很高兴和他见面的，但我没时间见他。 If your father had still been alive, he would have felt very proud of you. 你父亲如果还健在的话，他会为你骄傲的。