A. 高中英语情态动词
①只做情态动词:must,can,may……
②可做情态动词又可做实义动词：如：need,
dare
③具有情态动内词特容征：have(had,has)
to,used
to,
ought
to
④可做情态动词又可作助动词：如：shall(should),will(would)[
注意
mustn't代表强烈禁止
must表示主观，have
to表示客观。
美式英语中常用must
not
而不用
mustn't.
mayn't,mightn't和shan't也很少用
常用
can
(could),
may
(might),
must,
need,
ought
to,
dare
(dared),
shall
(should),
will
(would)
B. 高中语法情态动词
情态动词表推测
1 如果是疑问或者否定的话 语气最强烈的用法用Can。（我记得表示否版定的话也权可以用might的，但是这是特殊情况。一般大多用Can 或者could）
2 表示肯定的话 语气最强为must 还可以用may might不过只是语气强烈程度不同must语气最强接着是may下来是might
不能继续说了 再说我想LZ就晕了
C. 高中英语语法里的一个情态动词的一个题目
这句话首先说 你能弹奏很多乐器（Since you can play many musical instruments） 后面 有两个词要注意 一个是called 这里做认为。 第二版个是 accoomplishment 成就 还有一权个 well be 表被动
现在分别把这两个词带入句子 第一个是 必须被认为一个人的成就 而二个是可能被认为一个人的成就。 作为认为的主题 成就是不能被必须认为的。 不是带强制性的 所以 这里用may而不能用must
D. 高中英语语法：情态动词
情态动词有四类：
①只做情态动词：must,can(could),may(might)……
②可做情态内动词又可做实义动词：容need,dare
③具有情态动词特征：have(had,has)
to,used
to
④情态动词表猜测
E. 高中英语语法情态动词
shall 用在二三人称的陈述句中表 命令，威胁，允诺，警告 的语气You shall not leave your post . （表命令）回 问题中的答这句也是表命令的语气
用于一，三人称的疑问句表征求意见 Shall he go home now? Shall we go out for a walk?
F. 高中英语情态动词的用法有哪些
情态动词的考点精简
一、何谓“情态动词”？
情态动词主要用来表示说话人的情感、态度等，是中学英语语法的重点，也是高考的热点，是单项填空必考的一个知识点。高考试题常常借助语境和句子之间意义上的细微差别来考查学生对情态动词的基本用法及其区别，近五年高考中主要考查四点：情态动词表示推测和可能性的用法；情态动词与虚拟语气；情态动词的表达“情感、态度、语气等”，情态动词表示 “必要性”等方面的用法。
二、情态动词的特点
1.没有人称和数的变化。
2. 有些情态动词有过去式的变化:
e.g. will → would , can → could , may→ might , dare → dared
三、情态动词的否定形式
情态动词+ not +动词原形can not: can't , must not: mustn't , need not : needn't
四、情态动词的用法（常考考点）
Shall
一）用于一、三人称疑问句中，表示说话人征求对方意见和向对方请示。
Shall we begin our class? Shall he come in, sir? (征求对方意见)
二）用于二、三人称 表命令、许诺、警告、规定、威胁、决心、也用于宣布法律、规定的要求
1. You shall get my reply tomorrow. (许诺)
2. “The interest shall be divided into five parts, according to the agreement made by both side. （命令）
3. You shall be sorry for what you said one day, I tell you. (警告、威胁)
4. Nothing shall stop us from advancing. (决心)
5. —What does the sign over there read?
—“No person shall smoke or carry a lighted cigarette，cigar or pipe in this area.”(要求)
Should
一）应该，表示责任、义务
According to the air traffic rules, you should switch off your mobile phone before boarding.
二）竟然、（ 从句中） 惊奇、怀疑、不满(expect\, think, believe等词后） 委婉 客气（第一人称 ） 惊讶、埋怨 （二、三人称） 万一（ if 从句中）
1.） it’s a pity that he should be so careless. (竟然)
2.） I never expect that you should have come here. (惊奇 )
3.） I should advise you not to do it. (委婉 客气)
4.） Who should come to see you when you are in trouble! (埋怨 )
5.）If you should change your mind, please let me know. (万一)
三） 表示合理的推测
The video should be very interesting, in which you can see foreigners making Jiaozi ring the Spring Festival.
四）if 引导的虚拟条件句中，从句中只可出现should.
Should I have time, I would go there with you.
五）要求，命令和请求含义的动词后，接宾语从句，从句中谓语“should do”,should 可以省略
Tom suggested that I (should) go there at once.
六）should have done 本应该做但是没做
shouldn’t have done 本不应该做但是做了
You should have studied hard.
Must
一）表示必须要做的事: 必须
-Must I get to the station before three o'clock?
-Yes, you must. ( No, you needn't. )
二）用于指 偏要、硬要 （ 令人不快的事）
1. The car must break down just when we were in the jungle. (偏要)
2. -- Could I have a word with you, mum?
-- Oh, dear, if you must.
3. – Who is the girl standing over there?
-- Well, if you must know, her name is Mabel.
三）用于表肯定的猜测
He is absent today, and something must have happened to him.
She must be at home now, as I just called her.
四）禁止 (否定句)
You mustn’t make noises in the library. (禁止) (注：mustn’t没有表推测的意思)
Can\ could
一） 能力（陈述句）He can swim./ He could swim when he was a child.
二） 惊异、怀疑、不相信（否定、疑问、惊叹句）How can you be so careless？
三） can’t 表推测“一定不是” He can’t be Mr. White, because I don’t know him.
四） can/ could 用于否定和疑问表猜测 I lost my purse. Where could I have put it?
五） can 用于客观事实的推测，可能出现的某种现象
He is friendly, but sometimes he can be difficult to get along with.
The northern part of China is cold, but sometimes it can be warm.
Nowadays, graates can have difficulty finding jobs.
六） be able to do sth. 经过努力能达到
4. The fire in the hotel spread fast but fortunately all of the people were able to ran out. (经过努力能达到)
May \ might
一）祝愿（祈使句） May you return in safety. (祝愿)
二）可以（语气弱）. May I come in ? (可以)
三）表推测，不太可能的推测 Helen may go on the trip with us, but she isn’t quite sure yet.
四）may as well do sth. Now that you are here, you may as well try your best.
may well do sth. He may not well go with us—he hates travel.
五）might用于虚拟 If he came here tomorrow, he might have a chance of talking with her.
Will
一）意愿、决心、习惯性、倾向性、请求
1. I’ll do my best . (意愿)
2. I will never do such a thing again. (决心)
3. Fish will die without water. (习惯性、倾向性)
4. Will you give me a piece of paper? (请求)
二）区分于be going to, 表示没有计划，临时决定
---I’m sorry. I forgot to send the letter for you.
--- It doesn’t matter. I will go myself.
Would He promised he would never smoke again. (will的过去式)
Would you…? “I would like to… (婉转语气)
Last year our English teacher would sometimes tell us stories in English after class.
(过去的习惯动作,比used to正式，并没有“现已无此习惯”的含义。)
It would be about ten when he left home. (表料想或猜想)
Dare \ need
1. I dare to go there alone at night.
2. Do you dare to go there alone at night? = Dare you go there alone at night?
3. I don’t dare (to )go there alone at night. = I dare not go there alone at night.
dare say\ dare tell \ dare speak
4 needn’t have done 本没有必要做，但是做了
You needn’t have waited for her, as she didn’t go there.
情态动词+ do 表示对现在的推测
情态动词+ have done 表示对过去的推测（对过去的一种结果的假设或虚拟）
(1) should (not) / ought (not) to have done本（不）应该做某事，但却没有做或做了，含有责备或后悔之意。
例如： —I’m sorry. I _________at you the other day. B
—Forget it. I was a bit out of control myself.
A. shouldn’t shout B. shouldn’t have shouted
C. mustn’t shout C. mustn’t have shouted
(2) could have done本来能够做某事但未做。例如：
Thank you for all your hard work last week. I don’t think we ______ it without you. B
A. can manage B. could have managed
C. could manage D. can have managed
(3) needn’t have done本没有必要做某事但却做了。要注意needn’t do则表达“没有必要去做某事”，时间上应该是现在或将来。例如：
—Catherine, I have cleaned the room for you. B
—Thanks. You ________ it. I could manage it myself.
A. needn’t do B. needn’t have done
C. mustn’t do D. shouldn’t have done
(4)would (not) have done本来(不)会发生某事，但却（发生了）或没有发生。常用于虚拟条件句或含蓄虚拟条件引导的虚拟语气，表示对过去所发生事情结果的假设。例如：
He hesitated for a moment before kicking the ball, otherwise, he ________ a goal. D
A. had scored B. scored
C. would score D. would have scored
(5) might have done表示“本来可能……”，但实际上没有发生的事。例如：
What a pity! Considering his ability and experience, he ________ better. D
A. need have done B. must have done
G. 高中英语常见的情态动词且它们的意思
情态动词
★基本概念和用法：
情态动词是一类本身具有一定词义的动词，但没有人称和数的变化，也不能单独使用，它必须要和其他动词连用作句子的谓语。情态动词可表示语气、建议、要求、可能和意愿等。常用的情态动词有：can, could, may, might, must, shall, should, will, would, ought to, need, dare等。
★情态动词的基本用法
1. can (could) 表能力、允许、(从理论上或逻辑上判断）可能性以及表惊异、怀疑、不相信等态度（主要用于否定句、疑问句或感叹句中）。could指过去或表示语气委婉。例如：
The boy can speak three languages.这个孩子能说三种语言.
Can I borrow the book from the library?我能从图书馆里借书吗？
I could swim when I was eight.我八岁的时候就能游泳。
2. may (might) 表允许、可能性、祝愿等。might可以指过去，也可指现在，语气更委婉。例如：
May (Might) I ask for a photo of your baby?我可以要一张你孩子的照片吗？
She may be still waiting for us.她也许还在等我们呢。
May you have a happy holiday!祝你假期愉快！
3. will (would) 表意愿(用于各种人称的陈述句)、请求(用于疑问句)、某种倾向或习惯性动作等。would指过去或表示语气委婉。例如：
Will you come this way, please?请这边来。
Would you please close the window?请你关好窗子好吗？
Fish will die without water.鱼离开水会死。
Every time she was in trouble, she would go to him for help.每当她遇到麻烦，她都会找他帮忙。
4. must 表命令、推测（现在、过去或将来的猜测）、偏偏等含义。例如：
We must do everything step by step.你必须按部就班的做事情。
He must be ill. He looks so pale.他一定是病了，脸色看起啦这么苍白。
It can’t help. He must go with me.这不管用，他必须跟我走。
5. shall 用于第一、三人称疑问句中表示请求或征求对方意见; 用于第二、三人称陈述句中表示允诺、命令、警告、威胁、决心等。例如：
Shall I get you a cup of coffee?要我给你杯咖啡吗？
You shall have my answer tomorrow.明天你就能得到我的答复。
He shall be sorry for it one day, I tell you.我告诉你，他总有一天会为此后悔。
6. should / ought to 表义务（因责任、义务等该做）、推测、建议等。ought to 的口气比should稍重。例如：
You should be polite to your teachers.你应该对老师有礼貌。
You are his father so you ought to take care of him.你是他的父亲，因此你应该照顾他。
★情态动词的回答
疑问式
肯定回答
否定回答
Could I…?
Yes, you can.
Yes, go ahead.
No, you can’t.
Must I…?
Yes, you must.
No, you needn’t / don’t have to.
May I …?
Yes, of course.
Yes, please.
Yes, go ahead.
No, you mustn’t.
No, you can’t.
Will you ...?
Would you…?
Certainly. / Sure. / All right.
I’m sorry. I can’t.
No, thank you.
No, I won’t.
★辨析
1. can (could) 与be able to
can表示“能力”时，和be able to相当，许多场合都可以互换。但当叙述过去经过一番努力才能完成的事情或前面有特殊说明时，只能用be able to，且be able to可以用于各种时态。例如：
I can / am able to stand on my head.我能倒立。
I’m sorry I haven’t been able to answer your letter in time.非常抱歉我没有能够及时回答你的问题。
2. must与have to
must与have to都含有“必须”之意，must含有说话者的强烈决心 (表示主观的看法)，have to则表示外部因素或习惯使然 (即表示客观的必要，作“不得不”解)，且have to 有更多的时态形式。例如：
He said that he must work hard. （主观） 他说他必须努力学习。
My brother was very ill, so I had to call the doctor in the middle of the night. (客观) 妈妈病了，因此我不得不在半夜里叫医生。
We’ll have to help them as much as we can.我们将不得不尽力帮助他们。
3. would 与used to
would表示过去的习惯性动作时，只表示过去的情况，与现在无关，往往要带有一个特定的时间状语；used to可表示过去的习惯动作或状态，强调“现在已无此习惯”。例如：
Whenever we were in the country, we would play hide-and-seek in the fields. 无论什么时候我们在乡下，我们都会玩捉迷藏。
We used to play hide-and-seek in the fields.我们过去常在野外玩捉迷藏。
★ 情态动词+ have +过去分词
1) may(might) have + done sth, can (could) have + done sth.表示过去，推测过去时间里可能发生的事情。
Philip may (might) have been hurt seriously in the car accident. 菲利普也许在车祸中严重受伤的。
2)must have +done sth.，对过去时间里可能发生的事情的推测，语气较强，具有“肯定”的意思。
--- Linda has gone to work, but her bicycle is still here.琳达已经去工作了，但是她的自行车还在这里。
---She must have gone by bus.她一定是坐公车去的。
3) ought to have done sth., should have done sth. 本应该做某事，而事实上并没有做。否定句表示"不该做某事而做了"。
You ought to (should) have been more careful in this experiment.你在实验中本该更认真一点的。
He ought not to have thrown the old clothes away.你本不该旧衣服扔掉的。（事实上已扔了。）
注意：ought to 在语气上比should 要强。
4) needn’t have done sth 本没必要做某事
I dressed very warmly for the trip, but I needn’t have done so. The weather was hot.我穿的很暖和去度假，但是我没有必要这样穿，天气太热了。
H. 高中英语，情态动词
1. If The price of the goods _____ continue going up ,the socity would face a more difficult situation.
该题是对将来的条件虚拟，在条件从句中表示对将来的虚拟，谓语动词可以用三种形式表示：
1）动词的过去形式（动词 be 一般用 were 表示），如：
If The price of the goods continued going up ,the socity would face a more difficult situation. 假如货价真的在事实上有上涨的可能，...
2) were to + 动词原形，如：
If The price of the goods were to continue going up ,the socity would face a more difficult situation. 假如货价真的有上涨的计划，...
3）should + 动词原形, 如本题的选择：
If The price of the goods should continue going up ,the socity would face a more difficult situation.假如货价将来真的有可能上涨，...
注意：第三种一定是 should，这一点最容易与主句中的虚拟混淆。所以出现这种现象是由于条件虚拟从句的主句的谓语动词根据意思需要可以选择 should，would，might，could 或 ought to 加动词原形，所以常被初学者误以为条件句中也可以这样用。
2. ____ fired ,your health care and other benefit will not be immediately cut off.
该题与上一题一样，同样是条件虚拟句，所不同的是本题是省去连词 if 以后的倒装，恢复回 if 连接以后就会一目了然：
If you should be fired, your health care and other benefit will not be immediately cut off.
3. "The property ____ be divided into five farts ,according to the testament will made by Mr white" declared the judge.
本题是对情态动词的考查，区别如下：
A may ：用于表示可能性（也许）或者得到的允诺（允许）
B should 表示推测/推论（该是）或者是说话者的意愿“应该”
C must 表示推断或指具有较大的可能性（谅必/必定/肯定）或者义务（必须/应当）
D shall 用于陈述句第二、三人称, 表示说话者的意图、警告、命令、决心等, 主语的行动受讲话者支配。
题目中 The property shall be divided into five parts ...的主语是第三人称 property （财产），是由 judge （法官）宣布的判决。
I. 高中英语，关于情态动词使用
. 情态动词
.1 情态动词的语法特征
1） 情态动词不能表示正在发生或已经发生的事情，只表示期待或估计某事的发生。
2） 情态动词 除ought 和have 外，后面只能接不带to 的不定式。
3） 情态动词没有人称，数的变化，即情态动词第三人称单数不加-s。
4） 情态动词没有非谓语形式，即没有不定式，分词，等形式。
.2 比较can 和be able to
1）cancould 表示能力；可能 (过去时用could),
只用于现在式和过去式(could)。be able to可以用于各种时态。
They will be able to tell you the news soon. 他很快就能告诉你消息了。
2）只用be able to
a. 位于助动词后。
b. 情态动词后。
c. 表示过去某时刻动作时。
d. 用于句首表示条件。
e. 表示成功地做了某事时，只能用was/were able to， 不能用could。
He was able to flee Europe before the war broke out.
= He managed to flee Europe before the war broke out.
注意：could不表示时态
1）提出委婉的请求，（注意在回答中不可用could）。
--- Could I have the television on?
--- Yes, you can. / No, you can't.
2）在否定，疑问句中表示推测或怀疑。
He couldn't be a bad man.
他不大可能是坏人。
.3 比较may和might
1） 表示允许或请求；表示没有把握的推测；may 放在句首，表示祝愿。
May God bless you!
He might be at home.
注意： might 表示推测时，不表示时态。只是可能性比may 小。
2） 成语： may/might as well，后面接不带to 的不定式，意为"不妨"。
If that is the case, we may as well try.
典型例题
Peter ___come with us tonight, but he isn't very sure yet.
A. mustB. may C. can D. will
答案B. 表可能性只能用may.此句意可从后半句推出。
.4 比较have to和must
1)两词都是'必须'的意思，have to 表示客观的需要， must 表示说话人主观上的看法，既主观上的必要。
My brother was very ill, so I had to call the doctor in the middle of the night.我弟弟病得很厉害，我只得半夜里把医生请来。(客观上需要做这件事)
He said that they must work hard. 他说他们必须努力工作。（主观上要做这件事）
2)have to有人称、数、时态的变化，而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。
He had to look after his sister yesterday.
3） 在否定结构中： don't have to 表示"不必"
mustn't表示"禁止"，
You don't have to tell him about it. 你不一定要把此事告诉他。
You mustn't tell him about it.你一定不要把这件事告诉他。
.5 must表示推测
1) must用在肯定句中表示较有把握的推测，意为"一定"。
2) must表对现在的状态或现在正发生的事情的推测时， must 后面通常接系动词be 的原形或行为动词的进行式。
You have worked hard all day.You must be tired. 你辛苦干一整天，一定累了。（对现在情况的推测判断）
He must be working in his office. 他一定在办公室工作呢。
比较：
He must be staying there.
他现在肯定呆在那里。
He must stay there.
他必须呆在那。
3) must 表示对已发生的事情的推测时，must 要接完成式。
I didn't hear the phone. I must have been asleep.我刚才没有听到电话，我想必是睡着了。
4) must表示对过去某时正发生的事情的推测，must 后面要接不定式的完成进行式。
---Why didn't you answer my phone call?
---Well, I must have been sleeping, so I didn't hear it.
5) 否定推测用can't。
If Tom didn't leave here until five o'clock, he can't be home yet.如果汤姆五点才离开这儿，他此时一定还未到家。
.6 表示推测的用法
can, could, may, might, must 皆可表示推测，其用法如下：
1）情态动词+动词原形。
表示对现在或将来的情况的推测，此时动词通常为系动词。
I don't know where she is, she may be in Wuhan.
2）情态动词+动词现在进行时。
表示对现在或将来正在进行的情况进行推测。
At this moment, our teacher must be correcting our exam papers.
这时，我们老师想必在批改试卷。
3）情态动词+动词完成时。
表示对过去情况的推测。
We would have finished this work by the end of next December.
明年十二月底前我们很可能已完成这项工作了。
The road is wet. It must have rained last night.
地是湿的，昨天晚上一定下雨了。
4）情态动词+动词的现在完成进行时。
表示对过去正在发生事情的推测。
Your mother must have been looking for you.
你妈妈一定一直在找你。
5）推测的否定形式，疑问形式用can't, couldn't表示。
Mike can't have found his car, for he came to work by bus this morning.
迈克一定还没有找回他的车，因为早上他是坐公共汽车来上班的。
注意：could, might表示推测时不表示时态，其推测的程度不如can, may。
.7 情态动词+ have +过去分词
1) may(might) have + done sth, can (could) have + done sth表示过去，推测过去时间里可能发生的事情。
Philip may (might) have been hurt seriously in the car accident.
Philip can (could) have been hurt seriously in the car accident.
2)must have +done sth，对过去时间里可能发生的事情的推测，语气较强，具有"肯定"，"谅必"的意思。
---Linda has gone to work, but her bicycle is still here.
---She must have gone by bus.
3) ought to have done sth, should have done sth
本应该做某事，而事实上并没有做。否定句表示"不该做某事而做了"。
You ought to (should) have been more careful in this experiment.
He ought not to have thrown the old clothes away.（事实上已扔了。）
ought to 在语气上比should 要强。
4) needn't have done sth 本没必要做某事
I dressed very warmly for the trip, but Ineedn't have done so. The weather was hot.
5) would like to have done sth 本打算做某事
I would like to have read the article, but I was very busy then.
.8 should 和ought to
should 和ought to 都为"应该"的意思，可用于各种人称。
---Ought he to go?
---Yes. I think he ought to.
表示要求，命令时，语气由 should（应该）、had better最好）、must（必须）渐强。
.9 had better表示"最好"
had better 相当于一个助动词，它只有一种形式，它后面要跟动词原形。
had better do sth
had better not do sth
It is pretty cold. You'd better put on my coat.
She'd better not play with the dog.
had better have done sth表示与事实相反的结果，意为"本来最好"。
You had better have come earlier.
.10 would rather表示"宁愿"
would rather do
would rather not do
would rather… than… 宁愿……而不愿。
还有would sooner, had rather, had sooner都表示"宁愿"、"宁可"的意思。
If I have a choice, I had sooner not continue my studies at this school.
I would rather stay here than go home. = I would stay here rather than go home.
典型例题
----Shall we go skating or stay at home?
----Which ___ do?
A. do you ratherB. would you rather C. will you rather D. should you rather
答案B。本题考查情态动词rather的用法，would rather +do sth 意为"宁愿"，本题为疑问句，would 提前，所以选B。
.11 will和would
注意：
1）would like； Would like to do = want to 想要，为固定搭配。
Would you like to go with me?
2）Will you…?Would you like…? 表示肯定含义的请求劝说时，疑问句中一般用some, 而不是any。
Would you like some cake?
3）否定结构中用will，一般不用would, won't you是一种委婉语气。
Won't you sit down?
.12 情态动词的回答方式
问句肯定回答否定回答
Need you…?Yes, I must.No,I needn't
Must you…?/don't have to.
典型例题
1）---Could I borrow your dictionary?
---Yes, of course, you____.
A. mightB. will C. can D. should
答案C.could表示委婉的语气，并不为时态。答语中of course，表示肯定的语气，允许某人做某事时，用can和 may来表达，不能用could或might。复习： will 与you连用，用来提出要求或下命令。should与you 连用，用来提出劝告。
2）---Shall I tell John about it?
---No, you ___. I've told him already.
A. needn'tB. wouldn'tC. mustn'tD. shouldn't
答案A。needn't 不必，不用。 wouldn't 将不, 不会的。 mustn't 禁止、不能。 shouldn't不应该。本题为不需要，不必的意思，应用needn't。
3）---Don't forget to come to my birthday party tomorrow.
---______.
A. I don't B.I won't C. I can'tD. I haven't
答案B.will既可当作情态动词，表请求、建议、也可作为实义动词表"意愿、意志、决心"，本题表示决心，选B。
.13 带to 的情态动词
带to 的情态动词有四个：ought to, have to, used to, be to, 如加上have got to ,(=must), be able to，为六个。它们的疑问，否定形式应予以注意：
Do they have to pay their bill before the end of the month?
She didn't use to play tennis before she was fourteen.
You ought not to have told her all about it.
Ought he to see a heart specialist at once.?
ought to 本身作为情态动词使用。其他的词作为实义动词使用，变疑问，否定时，须有do 等助动词协助。
典型例题
Tom ought not to ___ me your secret, but he meant no harm.
A.have toldB.tellC.be tellingD. having told
答案A。由于后句为过去时，告诉秘密的动作又发生在其前因，此地应用过去完成时，但它在情态动词 ought to 后，所以用have。
.14 比较need和dare
这两词既可做实义动词用，又可做情态动词用。作为情态动词，两者都只能用于疑问句，否定句和条件句。 need 作实义动词时后面的不定式必须带to，而dare作实义动词用时, 后面的to 时常可以被省略。
1) 实义动词： need（需要, 要求）
need + n. / to do sth
2) 情态动词： need，只用原形need后加do，否定形式为need not。
Need you go yet?
Yes, I must. / No, I needn't.
3) need 的被动含义：need, want, require, worth（形容词）后面接doing也可以表示被动：
need doing = need to be done