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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。
第四章 情态动词（二）
一、 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．cancould 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cancould 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．shouldought 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。
第五章 动词不定式（一）
动词不定式是动词的一种非谓语形式，在句中不能单独作谓语。动词不定式具有动词的性质，它可以有自己的宾语和状语，从而构成动词不定式短语。它还可以有形式的变化，即一般式、进行式、完成式和被动式。同时，动词不定式也具有非动词的性质，相当于一个名词、形容词或副词，可以在句中担任主语、宾语、宾语补足语、表语、定语和状语。
一、动词不定式的特征和种类
动词不定式是由不定式符号to+动词原形构成，在某些情况下to也可省略。
A．不定式的一般式
不定式的一般式表示的动作通常与主要谓语的动作同时或几乎同时发生，或是在它之后发生。
He appears to be very happy.他看起来好像很高兴。（同时发生）
To catch the train, we'd better hurry to the station by taxi.为了赶上火车，我们最好赶紧乘出租车去车站。（to catch the train发生在hurry
to the station之后）
B．不定式的进行式
不定式的进行式表示正在进行的或与谓语动词同时发生的动作。
It happened to be raining when I got there.我到达那里的时候，天碰巧在下雨。
I'm glad to be traveling with you.我很高兴和你一起旅游。
C．不定式的完成式
不定式的完成式表示的动作在谓语表示的动作之前发生。
I'm sorry to have lost your key.我很抱歉把你的钥匙弄丢了。
I meant to have finished my work last night, but I didn't feel very
well.我本来想昨晚完成工作的，但是我感觉身体不舒服。
It has been an honor for me to have been invited to your country.对我来说，被邀请来你们国家是一件很荣幸的事情。
D．不定式的完成进行式
不定式的完成进行式表示的动作在谓语之前发生并且一直进行着。
He was said to have been living in London for twenty years.据说他在伦敦一直住了20年。
I'm sorry to have been interrupting you.很抱歉，我一直打扰你。
比较：
不定式的时态意义。
He is said to be studying abroad.据说他正在国外读书。（不定式的进行式表示动作正在进行）
He is said to have studied abroad.据说他在国外学习过。（不定式的完成式表示动作已经结束）
E．不定式的被动形式
当不定式逻辑上的主语是这个不定式表示的动作的承受者时，不定式一般要用被动形式。不定式的被动形式根据其与谓语动作发生的先后关系，有一般式和完成时两种。
1．一般式to be done
These are the books to be given out to the students.这些是要发给学生的书。
He asked to be sent to the place where he was most needed.他要求被派往最需要他的地方。
2．完成式to have been done
The novel is said to have been translated into many languages.据说这部小说已被译成多种语言。
He appeared to have been questioned for many times.看起来他已经被询问过很多次了。
F.不定式的否定形式
不定式的否定形式由not或never加不定式构成。
We decided not to go out because of the bad weather.由于天气不好，我们决定不出去。
Never to have made any mistake is impossible.从不犯错是不可能的。
注意：谓语动词的否定和不定式的否定不同的意义
I did not promise to wake him up.我没有答应叫醒他。
I promised not to wake him up.我答应了不叫醒他。
一、动词不定式的用法
动词不定式除了不能单独作谓语外，几乎能担任句子中所有的句子成分。
A．动词不定式作主语
不定式具有名词的特征，可在句子中充当主语。
1．不定式短语在句首作主语
To know
oneself is difficult.人贵有自知之明。
To say
is one thing and to do is another.说是一回事，做又是另一回事。
To love
and to be loved is the greatest happiness one can get.爱与被爱是一个人能获得的最大幸福。
2．用it作形式主语
在很多情况下，人们通常用it作为形式上的主语，而把不定式移到谓语之后，使句子结构显得平稳一些。
It's
rude to turn your back to your teacher and refuse to answer.背对着老师，拒绝回答问题是不礼貌的。
It is
impossible to learn a foreign language without making painstaking effort.想不下苦功就能学会外语是不可能的。
It
seemed a pity to have wasted so much time.浪费了这么多时间，真是遗憾。
注意：
当主语和表语都是不定式时，不能用形式主语代替动词不定式。
To
respect others is to be respected.尊重别人就是尊重自己。
To
become a slave is to give up one's freedom.做奴隶就等于放弃自由。
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