高中英语情态动词的用法一．can和could特别说明：（1）could用来表示请求时，语气委婉，主要用于疑问句，不能用于肯定句，答语应用can（即：could不能用于现在时态的简略答语中）。

如：——Could I use your dictionary?——Yes, you can.(否定回答可用：No, I’m afraid not.或者是you can’t)表示推测时，could不是过去式，只是语气更委婉；若是推测已发生的事或过去的情况，用can/could have done (2)can和be able to辨析can(could)和be able to都可以表示能力，意思上没有区别。

但can只有现在式和过去式，而be able to则有更多的形式。

如：I’ve always wanted to able to speak fluent English.Those bags look really heavy, are you sure you’ll be able to carry them on your own?但是，表示在过去某时的某一场合经过一番努力，终于做成了某事，通常不用could，而用was/were able to来表示。

这时，was/were able to相当于managed to do或succeed in doing。

如：After the accident it was a long time before she was able to walk again.The fire was very big, but most people were able to escape from the building.(3) 惯用形式“cannot …too…”表示“无论怎么……也不（过分）”。

如：You cannot be too careful.你越小心越好。

惯用形式“cannot but+ 不定式（不带to）”表示“不得不，只好”。

如：I cannot but admire her determination.我不得不钦佩你的决心。

二．may和might二．must和have to注意：表示”偏要，硬要做某事-how old are you, madam?-if you must know, I’m twice my son’s age(如果你非得知道，是我儿子年龄的两倍) 四．shall和should五．will和would特别说明：would与used to辨析would可用来表示过去反复出现的动作，但不能表示过去存在的状态，所以我们不能说：“she would be a quiet girl.”另外，would强调过去某种特定情况下的活动，是完全过去的事情，同现在没有联系。

而used to则着眼于过去和现在的对比，隐含现在已不存在，动作或状态都可表示。

Would可以表示不规则的习惯，used to则不可。

如：He used to be a naughty boy and cause trouble.I used to get up at six in the morning.Sometimes she would take a walk in the neighboring woods.In those days, whenever I had difficulties, I would go to Mr. Chen for help.六．need和dare七．ought的用法：说明：should与ought to 表示“应该”时的区别should 表示自己的主观看法，而ought to的语气中，含有“按道理应该……”之意。

若要反映客观情况或涉及法律义务和规定，一般用ought to。

如：You should help them with their work.You are his father. You ought to get him to receive good education.八．“情态动词+have done”用法被动语态1. 被动语态的基本时态变化被动语态通常为十种时态的被动形式, 被动语态由be＋过去分词构成，be随时态的变化而变化。

以do为例，各种时态的被动语态形式为：1) am/is/are +done (过去分词) 一般现在时例Visitors are requested not to touch the exhibits.2）has /have been done 现在完成时例All the preparations for the task have been completed, and we're ready to start.3）am/is /are being done 现在进行时例A new cinema is being built here．4）was/were done 一般过去时例I was given ten minutes to decide whether I should reject the offer.5）had been done 过去完成时例By the end of last year, another new gymnasium had been completed in Beijing.6）was/were being done 过去进行时例A meeting was being held when I was there.7）shall/will be done/ be going to be done/ be about to be done/ be to be to done一般将来时例Hundreds of jobs will be lost if the factory closes.8）should/would be done/ was\were going to be done/ was\were about to be done/was\were to be to done过去将来时例The news would be sent to the soldier's mother as soon as it arrived.9）shall/will have been done 将来完成时（少用）例The project will have been completed before July.10）should/would have been done 过去将来完成时（少用）例He told me that his new clothes would have been made very soon.2. 被动语态的特殊结构形式1)带情态动词的被动结构。

其形式为：情态动词＋be＋过去分词。

例The baby should be taken good care of by the baby-sitter.2) 有些动词可以有两个宾语，在用于被动结构时，可以把主动结构中的一个宾语变为主语，另一宾语仍然保留在谓语后面。

通常变为主语的是间接宾语。

例His mother gave him a present for his birthday.可改为He was given a present by his mother for his birthday.3) 当“动词+宾语+宾语补足语”结构变为被动语态时，将宾语变为被动结构中的主语，其余不动。

例Someone caught the boy smoking a cigarette.可改为The boy was caught smoking a cigarette.4）在使役动词have, make, get以及感官动词see, watch, notice, hear, feel, observe等后面不定式作宾语补语时，在主动结构中不定式to要省略，但变为被动结构时，要加to。

例Someone saw a stranger walk into the building.可改为A stranger was seen to walk into the building.5) 有些相当于及物动词的动词词组，如“动词＋介词”，“动词＋副词”等，也可以用于被动结构，但要把它们看作一个整体，不能分开。

其中的介词或副词也不能省略。

例The meeting is to be put off till Friday.3. 非谓语动词的被动语态v.+ing 形式及不定式to do 也有被动语态(一般时态和完成时态) 。

例I don't like being laughed at in the public.二、It is said that+从句及其他类似句型一些表示“据说”或“相信”的动词如believe, consider, expect, report, say, suppose, think等可以用于句型“It＋be＋过去分词＋that从句”或“主语＋be＋过去分词＋to do sth.”。

有：It is said that… 据说,It is reported that…据报道，It is believed that…大家相信，It is hoped that…大家希望，It is well known that…众所周知，It is thought that…大家认为，It is suggested that…据建议。

例It is said that the boy has passed the national exam.（＝The boy is said to have passed the national exam. ）三、谓语动词的主动形式表示被动意义1.英语中有很多动词如break，catch，clean，drive，lock，open，sell，read，write，wash等，当它们被用作不及物动词来描述主语特征时，常用其主动形式表达被动意义,主语通常是物。

例This kind of cloth washes well.注意：主动语态表被动强调的是主语的特征，而被动语态则强调外界作用造成的影响。

试比较：The door won't lock．（指门本身有毛病）The door won't be locked．（指不会有人来锁门, 指“门没有锁”是人的原因）2. 表示“发生、进行”的不及物动词和短语，如：happen, last, take place, break out, come out, come about, come true, run out, give out, turn out等以主动形式表示被动意义。