当主句的主语和从句的主语一致时且谓语动词为
语法进阶技巧定语从句的省略和引导词
语法进阶技巧定语从句的省略和引导词定语从句是英语语法中的一个重要部分，用来修饰一个名词或代词，并且在句中起到进一步说明的作用。
在定语从句中，有时可以省略一些词语或引导词，从而使句子更加简洁明了。
本文将介绍定语从句省略和引导词的进阶技巧。
定语从句的省略可以分为两种情况：省略引导词和省略关系代词。
首先，我们来看一下省略引导词的情况。
1. 当先行词是不定代词(all, any, some, none, something, anything等)时，定语从句引导词可以省略。
例句1: Is there anything (that) I can do for you？例句2: I have something (that) I want to show you.2. 当先行词是指示代词(this, that, these, those)或疑问代词(what, which, who, whom, whose, how, when, where, why)时，定语从句引导词可以省略。
例句1: The book (that) you recommended to me is very interesting.例句2: I don't know the reason (why) he left.3. 当先行词是不定代词或指示代词后面紧跟的名词是唯一的，且其功能与定语从句中的先行词在意义上是一致的时候，定语从句引导词可以省略。
例句1: I need a pen (that is) blue.例句2: She told me a story (that was) unbelievable.接下来，我们来看一下省略关系代词的情况。
1. 当关系代词在从句中作宾语时，且从句的谓语动词是及物动词时，可以将关系代词省略。
例句1: I have seen the man (whom/that) you are talking about.例句2: This is the book (which/that) I bought yesterday.2. 当关系代词在从句中作主语时，且从句的谓语动词是不及物动词时，可以将关系代词省略。
非谓语动词与状语从句的转化
非谓语动词与状语从句的转化非谓语动词与状语从句的转化状语从句是同学们在初中就掌握的内容，现将非谓语动词与状语从句之间转换的规律作一归纳，帮助大家更好地掌握非谓语动词。
一、非谓语动词与时间状语从句间的转换。
1 .当主、从句的主语一致，主、从句的谓语动作同时或L乎同时发生时，且从句中谓语动词是主动语态，可用现在分词的一般式转换。
如：When they heard the news，they jumped with joy.Hearing the news，they jumped with joy.当他们听到这则消息时，高兴得跳了起来。
2 .当主、从句的主语一致，从句中的动作发生在主句的动作之前或从句中谓语动词是完成时，可用现在分词的完成式转换。
如：After he(had)returned home，he began to work.Having returned home，he began to work.回到家以后，他开始工作。
3 .当主、从句主语一致时，由after，before，since，as soon as等引导的从句可分别用after/before/since/on加动名词短语转换。
如：Since I saw you last，I have been ill.Since seeing you last，I have been ill.自从我上次见你后，就一直在生病。
As soon as he heard this，he couldn’t help crying.On hearing this，he couldn’t help crying.他一听到这事，不禁哭了起来。
4 .当主、从句主语一致时，以when，while引导的从句，也可用when /while加现在分词短语转换。
如While we were walking along the river, we heard someone shouting.While walking along the river，we heard someone shouting当我们正沿着河走时,我们听到有人喊叫。
【备战高考】非谓语动词易错易混点
【备战高考】非谓语动词易错易混点一、单项选择非谓语动词1．When ___________ for his views about his teaching job, Philip said he found it very interesting and rewarding.A． asking C． having asked 【答案】 B B．asked D． to be asked【分析】试题剖析：句意:当马克被问做教师这个职业时的见解。
他说他发现这个工作是特别风趣和值得的。
这里when 指引的省略句，完好的是when he was asked his view about his job as a teacher ，这里当从句中的主语与主句的主语一致，并且从句的谓语动词有be时，这时从句的主语与be同时省略，应选B。
考点：考察省略的用法。
评论：此题难度适中。
为了使话说得简洁简要，英语句子中某个单词、短语甚至从句或主句都能够省去。
这类省去句子某些成分而保持句子意思不变的现象，称为省略。
它是高中阶段的重要的语法项目，需要考生认真剖析句子构造，来确立省略的内容。
这里考生简单误选A。
即学即练:He is rather difficult to make friends with, but his friendship， ______ is more true than any other.A.once gainedB.when to gainC.after gainingD.while gaining分析：A。
考察省略句。
once gained =" once" it is gained。
当状语从句的主语和主句的主语一致且从句中含有be 动词时，可省略从句中的主语和谓语部分。
2．A hearty laugh relieves physical tension, _____your muscles relaxed for over half an hour. A． to leave B． left C． leaving D． leave【答案】 C【分析】【详解】考察非谓语动词。
从句的省略规则
从句的省略规则从句是在句子中充当一个整体，起到修饰、表达具体含义的作用。
在使用从句的时候，有时候可以采用省略规则，即省略一些不必要或重复的成分，使句子更加简洁明了。
本文将介绍从句的省略规则，帮助读者更好地理解和运用这一语法现象。
一、主语从句的省略在主语从句中，如果主句的主语与从句的主语一致，且从句的谓语动词是be动词（am，is，are，was，were），可以将从句的主语省略。
例句1：That he is talented is well known.（从句的主语he省略）例句2：Whether she can come or not is still unknown.（从句的主语she省略）二、宾语从句的省略在宾语从句中，如果从句的主语和主句的宾语一致，且从句的谓语动词是be动词，可以将从句的主语和be动词省略。
例句1：I don't know if he's ready.（从句的主语he和be动词省略）例句2：She wonders whether it's true or not.（从句的主语it和be动词省略）三、宾语补足语从句的省略在宾语补足语从句中，如果从句的主语和主句的宾语补足语一致，且从句的谓语动词是be动词，可以将从句的主语和be动词省略。
例句1：They elected him chairman, which was a wise choice.（从句的主语which和be动词省略）例句2：We made her the team captain, which turned out to be a mistake.（从句的主语which和be动词省略）四、定语从句的省略在定语从句中，当从句的主语和关系代词或关系副词引导的介词宾语一致时，可以将从句的主语和关系代词或关系副词省略。
例句1：The book I borrowed from the library is very interesting.（从句的主语I省略）例句2：The girl I saw at the party is my best friend.（从句的主语I省略）五、状语从句的省略在状语从句中，当从句的主语和主句的主语一致，且从句的谓语动词是be动词，可以将从句的主语和be动词省略。
省略和倒装语法解释
多变的省略句掌握好省略句，应注意以下几条：1.感官动词或使役动词（如：notice, hear, let, make)等后接不定式作宾补时省略to,被动时to不能省略。
2.在prefer to do rather than…, cannot help but…do, nothing …but等句型中常省略to。
3.为避免重复，作某些动词（hope, want)等宾语或（tell, order, ask)的宾补时，省略不定式短语，只保留to.4.应注意状语从句、定语从句中的省略。
5.注意not ,so ,neither, nor的“替代性”省略。
6.状语从句中，如果谓语含动词be,主语又与主句主语一致或主语是it,从句中主语和be一齐省略。
7.常见的省略形式：（1）If （it is）possible[如果可能的话]；（2）If (it is) necessary[如果必要的话];（3）If any: 例: Correct the mistakes in the passage if (there is) any (mistakes)比较:Do you have anything to say? (不知道对方是否有话要说,) Do you have something to say?(认为对方有话要说.)一、替代省略1. 用it, one, that，ones, those替代句子中重复出现的名词、代词或句子。
one是指代同名称的另一样东西(同类异物),代替前面句子中重复出现的可数名词;that替代特指可数或不可数名词,后面常跟有in或of短语作后置定语;it指代同名称的同样事物(同类同物)。
例:One took a taxi, and the other walked home. I haven’t a book, can you lend me one？2."So / Nor(Neither)+谓语+主语"这种句型是用来替代前面提到的情况,表明它也适用于后者。
宾语从句(5)
Robert saw what Mr.Smith did. ＝Robert saw everything (that) Mr.Smith did.
解析：由this morning可知事情发生在过去，故排除C、D两项；宾语从句
应用陈述句语序。
答案： B
高频考向四 宾语从句的否定前移 在宾语从句中，当主句的谓语动词为think，believe，expect，imagine， suppose等时，如果主句为I或we时，从句中表示否定意义的not应移到think ，believe，expect，imagine，suppose等前。如： I don't suppose he will come.我猜他不会来。 【注意】如果主句主语不是I或we，则not不前移。如： She thinks she can't arrive there on time.她认为她不能按时到那儿。 【例7】 翻译：我认为明天不会下雨。
高频考向一 宾语从句的引导词
①宾语从句是陈述句，引导词用that，在口语中that可以省略。如： We believe(that)he is honest.我们相信他是诚实的。 ②如果宾语从句由一般疑问句转换而来，其引导词用if或whether。一 般情况下，二者可以通用，但从句中有or not或从句充当介词的宾语时， 只能用whether。如： I don't know if/whether she will come here.我不知道她是否将来这儿。 Sorry，I don't know whether he will come or not.对不起，我不知道他是 否会来。 ③宾语从句是特殊疑问句时，引导词就是特殊疑问词。如：
高中英语状语从句省略现象单选题40题
高中英语状语从句省略现象单选题40题1. When ______ in the library, keep quiet.A. studyingB. studiedC. to studyD. study答案：A。
本题考查时间状语从句的省略。
When 后接现在分词studying，表示“当正在图书馆学习时”，其完整形式为When you are studying in the library。
B 选项studied 表示被动，不符合语境；C 选项to study 表示目的，“为了学习”；D 选项study 形式错误。
2. While ______ TV, I heard a knock at the door.A. watchedB. watchingC. was watchingD. watch答案：B。
这里是时间状语从句的省略，While 后接现在分词watching，表示“当正在看电视时”，完整形式是While I was watching TV。
A 选项watched 是过去分词，表被动；C 选项was watching 是完整的谓语形式，此处省略了主语和be 动词；D 选项watch 形式错误。
3. When ______ to answer the question, he remained silent.A. askedB. askingC. to be askedD. ask答案：A。
When 后接过去分词asked，表示“当被问到回答这个问题时”，完整形式是When he was asked to answer the question。
B 选项asking 表示主动，不符合；C 选项to be asked 表示将来被动；D 选项ask 形式错误。
4. ______ crossing the street, look around carefully.A. WhileB. WhenC. AsD. Before答案：B。
高中英语状语从句省略现象单选题40题(含答案)
高中英语状语从句省略现象单选题40题(含答案)1. When _____, the museum is very beautiful.A. lightingB. litC. is litD. being lit答案：B。
本题考查时间状语从句的省略。
完整的句子是When it is lit，这里省略了it is，lit 在这里是过去分词表被动。
A 选项lighting 是现在分词，主语应该是人，而不是博物馆；C 选项多了is；D 选项being lit 多了being，显得多余。
2. While _____ in the library, he found a rare book.A. readingB. readC. is readingD. being read答案：A。
When/While + 现在分词短语表示时间状语从句的省略，完整的句子是While he was reading in the library。
B 选项read 是过去式或过去分词，形式错误；C 选项多了is；D 选项being read 是被动形式，不符合语境。
3. After _____ his homework, he went out to play.A. finishB. finishingC. finishedD. being finished答案：B。
After + 现在分词短语表示时间状语从句的省略，完整的句子是After he finished his homework。
A 选项finish 是动词原形，形式错误；C 选项finished 单独使用不能表省略；D 选项being finished 是被动形式，不符合语境。
4. Before _____ to bed, she read a story.A. goB. goingC. wentD. being gone答案：B。
Before + 现在分词短语表示时间状语从句的省略，完整的句子是Before she went to bed。
状语从句与非谓语动词的转化(写作)
状语从句与非谓语动词的转化一、非谓语动词与时间状语从句间的转换。
1.当主、从句的主语一致，主、从句的谓语动作同时或几乎同时发生时，且从句中谓语动词是主动语态，可用现在分词的一般式转换。
如： When they heard the news，they jumped with joy.Hearing the news，they jumped with joy.2.当主、从句的主语一致，从句中的动作发生在主句的动作之前或从句中谓语动词是完成时，可用现在分词的完成式转换。
如： After he(had）returned home，he began to work.Having returned home，he began to work.3.当主、从句主语一致时，由after，before，since，as soon as等引导的从句可分别用after/before/since/on加动名词短语转换。
如： Since I saw you last，I have been ill.Since seeing you last，I have been ill.As soon as he heard this，he couldn’t help crying.On hearing this，he couldn’t help crying.4.当主、从句主语一致时，以when，while引导的从句，也可用when /while加现在分词短语转换。
如While we were walking along the river, we heard someone shouting.While walking along the river，we heard some one shouting.5.当主、从句的主语一致，且从句的谓语动词是被动语态时,可用过去分词短语转换。
如:After they were sent to the zoo, the monkeys had good health. Sent to the zoo, the monkeys had good health.6.当主、从句的主语不一致时，时间状语从句可转换成分词的独立主格结构，即名词/主格代词＋分词。
高二英语省略句在状语从句中的用法单选题20题
高二英语省略句在状语从句中的用法单选题20题1. When ______ in the library, keep quiet.A. beingB. to beC. areD. /答案：D。
本题考查时间状语从句中的省略。
当从句的主语和主句主语一致，且从句中有be 动词时，可以省略从句的主语和be 动词。
本句完整形式为“When you are in the library”，省略了“you are”，所以选择D 选项。
A 选项“being”表示正在进行的动作，不符合语境；B 选项“to be”表示将来的动作，也不符合；C 选项“are”若使用，则从句缺少主语。
2. While ______ TV, she heard a strange noise.A. watchedB. watchingC. watchD. to watch答案：B。
在时间状语从句中，当从句的主语和主句主语一致，且谓语动词含有be 动词时，可以省略主语和be 动词。
本句完整形式为“While she was watching TV”，省略了“she was”，所以用“watching”，选择 B 选项。
A 选项“watched”是过去分词，不能作状语；C 选项“watch”是动词原形，不能直接作状语；D 选项“to watch”通常表示目的，不符合语境。
3. When first ______ to the market, these products enjoyed great success.A. introducingB. introducedC. introduceD. being introduced答案：B。
本句完整形式为“When these products were first introduced to the market”，从句的主语和主句主语一致，且从句中有be 动词，省略了“these products were”，用过去分词“introduced”，表示被动和完成，选择 B 选项。
高中英语状语从句省略现象单选题40题
高中英语状语从句省略现象单选题40题1.When ______ in the library, we should be quiet.A.readB.readingC.to readD.having read答案：B。
本题考查时间状语从句的省略。
当主句和从句的主语一致，且从句谓语动词含有be 动词时，可以省略从句的主语和be 动词。
这里完整的句子是When we are reading in the library，省略we are 后变为when reading in the library。
A 选项read 形式错误；C 选项to read 表目的，不符合语境；D 选项having read 表示完成，也不符合语境。
2.______ the bell rang, the students rushed out of the classroom.A.As soon asB.WhileC.SinceD.Until答案：A。
as soon as 引导时间状语从句，表示“一……就……”。
while 表示“当……的时候”，通常强调动作的同时性；since 表示“自从”；until 表示“直到……才”。
这里“铃一响，学生们就冲出教室”，A 选项符合语境。
3.I was doing my homework ______ my mother came back.A.whenB.whileC.asD.since答案：A。
when 既可以表示某个具体的时刻，也可以表示一段时间。
while 强调动作的同时性；as 强调伴随；since 表示“自从”。
这里表示“我正在做作业的时候妈妈回来了”，用when。
4.______ time goes by, we become more mature.A.AsB.WithC.SinceD.Because答案：A。
as 引导时间状语从句，表示“随着”。
with 后面不能接句子；since 表示“自从”；because 表示原因。
(英语)高考英语非谓语动词真题汇编(含答案)含解析
（英语）高考英语非谓语动词真题汇编( 含答案 ) 含分析一、单项选择非谓语动词1．（北京） During the Mid-Autumn Festival, family members often gather together _________a meal, admire the moon and enjoy moon cakes.A． share B． to shareC． having shared D． shared【答案】 B【分析】观察非谓语动词。
句意：在中秋节时期，家人们往常汇聚在一同吃饭，观月，品尝月饼。
gather 是谓语动词，“_________ a meal, admire the moon and enjoy moon cakes是”状语，家人聚在一同的目的是吃饭，观月，品尝月饼，表目的用动词不定式，故 B 选项正确。
点睛：动词不定式能够做主语，状语，定语，宾语，表语等。
动词不定式做目的状语时，能够置于主句从前也能够置于主句以后，往常译为“为了”。
2．（天津） I need a new passport so I will have to have my photographs___________.A． taking B． takenC． being taken D． take【答案】 B【分析】观察非谓语动词。
句意：我需要一个新护照，所以我将不得不摄影片。
此题观察非谓语动词作宾语补足语，宾语 my photograph 与补足语之间为被动关系，故用过去分词作宾语补足语。
C 项表示正在进行。
应选 B。
点睛：此题观察的非谓语动词为高中要点语法之一。
在剖析题目的时候，第一要抓住非谓语动词在句中所作的成分，找出该非谓语动词所对应的逻辑主语，再剖析两者之间的关系，最后依据句意选择正确的答案。
3．115． ______ his love, Chris sent his mom a thank- you note on Mother’ s Day.A． ExpressingB．Expressed C． To express D． Having expressed【答案】 C【分析】观察动词不定式。
专题21 语法填空之特殊句式专项-2022年高三英语一轮复习之语法填空
语法填空之特殊句式专项1．I made him ________(repeat) his promise.2．It wasn’t until nearly a month later ________ I received the manager’s reply.3．It was only after he had read the papers ________ Mr.Gross realized the task before him was extremely difficult to complete.4．While __________(discuss) the plan, they found it practical.5．The boy did nothing but_________(wait) for the police in the tree.6．The hurricane caused more damage than_________(expect).7．When ________(design) the new tower，he came up with such an extraordinary idea. 8．There________ (be)no milk in the fridge. Could you get some for me, Dick?9．The boy is running impatiently here and there as if ________ (search) for something lost on the sports ground.10．Will you be free this evening? If________ , let's go to the concert together.11．This is one of the oldest buildings in town, if ________ the oldest.12．Not only ________ television attract those who can read but those who can't. 13．When deeply ______ (absorb) in work, my head teacher always forgets all about eating and sleeping.14．No until he took off his glasses ________ I recognize him.15．If ______ (take) good care of, the bird can live as long as twenty years.16．So energetic ________the boy that he never stopped moving.17．Gone __________(be) the days of searching shop after shop for the perfect pair of boots.18．It was because I was stuck in the traffic ________ I came late.19．While ________(work) there, out of a strong passion for knowledge, he continued to study, earning a doctorate in physics in 1905.20．Video games can be a bad influence if ________ (leave) in the wrong hands. 21．When _________ (heat), ice will be changed into water.22．Though _________ (warn) of the danger, he still went skating on the thin ice.23．Not only ________ she make a promise, but she also kept it.24．If ________(take) according to the instructions, the new medicine has almost no side effects.25．During the __________(rain)season, it is along these waterways __________ rainwater moves down the mountains and into the terraces ．26．Many kids develop problems from finger sucking (吮吸手指) that can cause lifelong problems unless ________ (treat) properly.27．One day after school, while ________ (explore) the green woods of this magnificent mountain, I almost fell on a set of stairs.28．There are few, if ________, mistakes in the book.29．________ was not until he came back from Africa that year that he met the girl he would like to marry.30．It was my sister ________ helped me out when I was in trouble.31．I________ (do) telephone you last night.32．You may change the form ________ necessary.33．The new technology, if ________ (apply) to rice growing, will help increase the grain output.34．There ________ a great number of students entering for the exam, and the number of them ________ increasing nowadays. (be)35．Though ____________ (injure) in the accident, the bus driver did all he could to help the passengers to safety.36．Jane Goodall finds that there ________ (be) a strong bond between members of a chimp family.37．On the contrary, think it is Truman, rather than you, that ________(be) to blame. 38．Under no circumstances ________ you ________（leave）the door to the Data Centre unlocked.39．He always prefers to start early rather than__________（leave）everything to the last minute.40．Every evening after dinner, if not _________ (tire) from work, I will spend some time walking my dog.41．Experts warn that medical waste from hospitals, if not ________（handle）properly, may contribute to spreading diseases.42．He arrived earlier than ________ (expect).43．She gave me a comforting smile, nodded while________(listen) patiently.44．What is it ________ helps make virtual reality a more usable and accessible technology?试卷第2页，总3页45．These flowers will die unless ________ (water) every day.46．It was at nine o’clock ________ we began to watch TV.47．Though ________ (warn) of the danger, Jack still went swimming in the lake. 48．Though ________ (lack) in confidence, Tom made every effort and his dream came true at last.49．Though ________(bury) in books these days, I have still joined several student clubs in order to improve myself.50．When deeply ________ (absorb) in work, the scientist always forgets all about eating or sleeping.参考答案1．repeat【详解】考查非谓语动词。
高三英语状语从句省略用法单选题30题
高三英语状语从句省略用法单选题30题1.When _ at the airport, she found her passport missing.A.arrivedB.arrivingC.having arrivedD.arrive答案：B。
本题考查时间状语从句的省略用法。
当主句和从句的主语一致，且从句中含有be 动词时，可以省略从句中的主语和be 动词。
此句中，she 和arrive 是主动关系，所以用arriving。
A 项arrived 表示被动或过去完成，不符合；C 项having arrived 强调先后顺序，此处不需要；D 项arrive 形式错误。
2._ the bell rang, the students rushed out of the classroom.A.ImmediatelyB.No sooner hadC.As soon asD.Hardly when答案：C。
A 项immediately 可作连词引导时间状语从句，当从句主语和主句主语一致时，可以省略主语和be 动词，但此处未体现省略用法，且意思不如as soon as 直接；B 项no sooner had 需倒装，与题干不符；D 项hardly when 也需倒装，不符合要求。
as soon as 引导时间状语从句，符合语法规则。
3._ she heard the news, she burst into tears.A.The momentB.At the momentC.For the momentD.In a moment答案：A。
the moment 可以引导时间状语从句，相当于as soon as。
B 项at the moment 表示“此刻”，不是连词；C 项for the moment 表示“暂时”，不是连词；D 项in a moment 表示“一会儿”，不是连词。
4._ he came in, I was reading a book.A.WhileB.WhenC.AsD.All of the above答案：D。
定语从句的省略
定语从句的省略定语从句是英语中常用的修饰名词的从句形式，用来进一步描述或限定名词的性质、特征等。
通常，定语从句由一个引导词引导，并且在从句中有一个动词，一个主语等。
然而，在一些情况下，我们可以省略定语从句中的部分内容，从而简化句子的结构，使语言更加简洁。
本文将介绍定语从句的省略规则和注意事项。
一、定语从句的省略规则1. 省略引导词和be动词在定语从句中，如果从句中的主语和主句中的主语一致，并且从句中的谓语动词是be动词，那么我们可以省略引导词和be动词。
例如：The car that is parked outside is mine.The car parked outside is mine.2. 省略关系代词who/whom/which当定语从句的关系代词在从句中作宾语时，可以省略。
例如：The girl who(m) I saw yesterday is my neighbor.The girl I saw yesterday is my neighbor.3. 省略关系代词whose关系代词whose表示所有关系，当其后修饰的名词为物时，可以省略。
例如：The book whose cover is torn belongs to me.The book with the torn cover belongs to me.4. 省略关系代词where/when当定语从句中的关系代词是where或when时，可以省略。
例如：This is the school where I studied for four years.This is the school I studied for four years.二、定语从句的省略注意事项1. 定语从句的省略是为了简化句子结构，使其更简洁明了。
但在使用时需要注意不影响句子的准确性和清晰度。
2. 省略定语从句的同时，也要确保句子的语义不会产生歧义。
高中英语时间状语从句结构单选题40题
高中英语时间状语从句结构单选题40题1.She was reading a book when the phone rang.A.whenB.whileC.asD.before答案：A。
本题考查时间状语从句引导词的用法。
“when”表示“当……的时候”，强调动作的突然性。
句中“她正在读书的时候电话响了”，动作有突然性，所以用“when”。
“while”强调动作的同时性，“as”也强调动作的同时性，“before”表示“在……之前”，不符合题意。
2.He was taking a shower while his mother was cooking.A.whenB.whileC.asD.after答案：B。
“while”强调动作的同时性，句中“他在洗澡的时候他妈妈在做饭”，两个动作同时进行，所以用“while”。
“when”强调动作的突然性，“as”也强调动作的同时性但不如“while”强烈，“after”表示“在……之后”，不符合题意。
3.The sun was shining as we walked along the beach.A.whenB.whileC.asD.since答案：C。
“as”强调动作的同时性，句中“当我们沿着海滩走的时候太阳正照耀着”，两个动作同时发生，所以用“as”。
“when”强调动作的突然性，“while”强调动作的同时性但更侧重较长时间的同时进行，“since”表示“自从……以来”，不符合题意。
4.I was doing my homework when my friend came to see me.A.whenB.whileC.asD.until答案：A。
“when”表示“当……的时候”，强调动作的突然性。
句中“我正在做作业的时候我的朋友来看我了”，动作有突然性，所以用“when”。
“while”强调动作的同时性，“as”也强调动作的同时性，“until”表示“直到……才”，不符合题意。
While用法,
While⽤法, while表⽰只要While⽤法2. while表⽰当......的时候、在......期间,是从属连词,引导时间状语从句,当从句的主语和主句的主语⼀致,且谓语中含有be时,可以省略从句的主语和be。
例如:While we were talking Mr Wang came in. 我们在谈话时,王先⽣进来了。
You don”t go home while (you are) studying. 在学习期间,你不要回家。
2) while表⽰虽然......但是......、尽管......还......,是从属连词,引导让步状语从句,相当于though。
例如;While she loves her students, she is very strict with them.虽然她爱她的学⽣,但是她对他们很严格。
While I admit his good point, I can see his shortcoming.尽管我承认他的优点,我还能看到他的缺点。
3) while表⽰只要,是从属连词,引导条件状语从句,相当于as / so long as,可放在句⾸或句中。
例如:There will be life while there is water and air. 只要有⽔和空⽓,就有⽣命。
You don”t have to worry while we are here. 只要我们在这⼉,你就别着急。
4) while表⽰趁着,是从属连词,引导时间状语从句。
例如:While the roses are yet in bloom, will you come with me to see them?趁着玫瑰花还开着,你和我⼀道去看看好吗?Strike while the iron is hot. 趁热打铁。
5) while表⽰然⽽、但、却,作并列连词⽤,连接并列句,使前后两句构成转折和对⽐关系。
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当主句的主语和从句的主语一致时且谓语动词为be，常省略从句的主语和be动词.
省略的条件: (1)从句中被省略的主语必须与主句的主语一致,或者是it；(2)谓语动词必须含有be；(3)从句必须与主语和be动词一起省去，不可只省略主语而保留整个谓语，也不可只保留主语而省略谓语。
1. 由when/while/as/once/whenever/as soon as引导的时间状语从句
例：Please come here as soon as（it is）possible.
While （I was——walking in the rain, I heard my name called. 我在雨中漫步时，听到有人叫我的名字。
2.由if/unless引导的条件状语从句例：She won’t come to party unless（she is）invited.
3.由though/although/even if/even though引导的让步状语从句
例：He is very good at painting, though（he is）very young. T hough（he was）exhausted, he stayed up late. 尽管疲惫不堪，他仍很晚才睡。
4.由because引导的原因状语从句
例：He was praised because （he was）brave.
5. 由wherever/where引导的地点状语从句
例：Fill in the blanks with articles where（it is）necessary.
6.从句和主句中相同或大体相同部分都可以省略
例：The sooner, the better. 越早越好。
She is as tall as I. 她和我一样高。
7.由as if/as though/as 引导的方式状语从句
例：The boy looked as if（he was）afraid of nothing.
I wonder why he didn’t do as（he was）told to.
8.比较状语从句省略相同的部分：
例：She likes reading better than (she likes) going to parties.
He has lived here longer than I (has lived).
In winter it is colder in Beijing than（it is）in Guangzhou.。