三.语法知识：非谓语动词(不定式)
动词不定式的形式及特点
动词不定式一般由to+动词原形构成，其否定式是not to do.
动词不定式的用法：
1． 作主语
1).可以直接作主语,谓语动词需用单数。如： To see is to believe．
练一练：To study English hard ______ very important.
2).但在英语中，常用it作形式主语，真正的主语即动词不定式放在后面，避免头重脚轻，如：
It's wrong to play tricks on other people．
It's our duty to keep our environment clean and tidy．
规律：动词不定式在句中作主语时，常放在It is ＋adj．（形容词）＋to do sth．或 It is ＋n．（名词）＋to do sth．句型中，it仅作形式主语,真正的主语是动词不定式。
练一练：It’s so easy for me _____ _____ (do) that.
It’s necessary for you _____ ______(lock) the car when you do not use it.
It’s my turn _____ ______ (clean) the classroom.
2．作宾语
1)Want decide ，agree ,ask,hope,wish,learn,expect,pretend,refuse,promise,等动词后面跟并且只能跟不定式。如：
We agreed to start early．
She wants to be a doctor．
2).love，like ，begin，start，hate ，prefer等词后面可以接不定式。
规律：上述动词后面除接不定式外，还可以接动名词，意思无很大区别。
提示板：like doing指经常性动作，而like to do指一次性的动作。如：
I like swimming，but I don't like to swim now．我喜欢游泳，但我现在不想游。
3).stop，forget，remember，go on ，try等词或短语后面可以接不定式，还可以接动名词。
规律：上述动词后面接不定式和接动名词意思大不相同。
提示板：
1.stop to do sth．：停止一件事，去做另一件事。
stop doing sth．：停止正在做的事。
2.forget to do sth表示“忘记”将要做的事
forget doing sth表示“忘记”曾经做过的事
3. remember to do 意思是记住去做某事,表示这件事情还没有做.
remember doing 意思是记得做过某事,表示这件事情还已经做了
4. stop to do sth．：停止一件事，去做另一件事。
stop doing sth．：停止正在做的事。
5.go on doing sth 是指继续做同一件事，
go on to do sth 是指继续去做另一件事
6. try to do sth.尝试去做某事 try doing sth. 尽力做某事
练一练：
1、I forgot _____________ (ask) Tom. 我忘了去问汤姆。
2、I’ll never forget _________(meet) you that afternoon. 我永远不会忘记那天下午见到你的情况。
3、Remember____________( turn off) the lights when you leave the room. 在你离开房间之前,记得把灯关了.
4、I remembered______________( turn off) the lights when I left the room. 我记得我关灯了,当我离开房间的时候.
5、After having a rest,I went on _______(do) homework. 休息一会后，我继续做作业.（休息前就在做此事）
6.After cleaning the floor,I went on ______ (clean) the window. 擦完地后，我又继续擦玻璃.
4).在find／feel＋it＋adj．＋to do sth．句型中，it是形式宾语，真正的宾语是后面的动词不定式。如：
The man downstairs found it difficult to get to sleep．
I feel it easy to recite the text．
练一练：
He finds it interesting ______ (read) the book
They feel it hard ________ (finish) the task on time.
3．作宾语补足语
1).tell，ask，want，order，teach，invite，warn，wish，help，get，wish，help等词后面常接不定式作宾补。如：
I tell him not to go there by bus ．
Edison's mother taught him to read and write．
2).let，make，have，see，hear，feel，watch， notice后面接不带to的不定式作宾补。如：
The boss makes them work 16 hours a day． I heard her sing in the next room．
提示板：若变成被动语态，在上述结构中，不定式符号to要加上。如：
They are made to work 16 hours a day by the boss．
She was heard to sing in the next room．
练一练：
Though he often _______(make) his sister cry, today he was ________ (make)cry by his sister.尽管他总是弄哭他妹妹，今天却被妹妹弄哭了。
They ask her ______( leave )the country.
4．作定语：放在被修饰的名词、代词后面
例句：I have a lot of work to do．
The doctor said he could do nothing to help the boy．
规律：动词不定式若在句中作定语，常放在被修饰的名词、代词之后。
提示板：如果动词不定式和前面所修饰的词构成动宾关系，若动词是不及物动词，切记不要忘掉介词。如：
I have a small bedroom to live in．
Have you got some pens to write with？
练一练：
①The next train ________ (arrive) is from Washington.
②Have you anything to be taken to your sister?
③Do you have anything _______( say) on the question?
④Would you please give me some paper ________(write )on?
⑤My wish ______( visit) France has come true at last.
5．表语：放在be动词,感官动词，三变turn, become,get,后面
例句：His wish is to become a scientist．
The first important thing is to save the soldiers' lives． 当务之急是抢救战士们的生命。
规律：动词不定式在句中作表语时，通常对连系动词前面的名词进行诠释说明。
My work is _______(clean )the room every day.
6.作状语：修饰动词，表目的，结果，原因。
To catch the bus, I got up early.
7.不定式和疑问词连用作宾语。
When to do/ How to do /What to do/Why to do/Where to do/Which to do
例如：Do you know how to get to the zoo? 你知道怎么到动物园吗