辨析before和since

英语介词知识总结归纳英语介词知识总结归纳篇一一、表示时间的介词时间介词有in , on，at，after，since，during,by,before,after,until等，前三个介词用法有个口诀：at午夜、点与分，上午、下午、晚用in。

年、月、年月、季节、周，之前加上介词in。

将来时态多久后，这些情形亦用in。

日子、日期、年月日，星期之前要用on。

其余几组常见的时间介词辨析如下辨析如下：1、时间介词in与after的用法辨析介词in +一段时间用于一般将来时。

如：We’ll go to school in two weeks.介词after +一段时间用于一般过去时。

如：My mother came home after half an hour.介词after +时间点常用于一般将来时。

如：We’ll go out for a walk after supper.2、时间介词for与since的用法辨析介词for表示一段时间如：I have been living here for 10 years.介词since表示从过去某一时间以来如：I have been living here since 2000.3、时间介词before与by的用法辨析介词before表示“在…之前”如：He won’t e back before five .介词by表示“到…时为止，不迟于…”如：The work must be finished by Friday.4、时间介词during与for的用法辨析当所指的时间起止分明时用介词during如：He swims every day during the summer.如果一段时间不明确则用介词for如：I haven’t seen her for years.5、时间介词till与until用法的异同till和until用在肯定句中，均可表示“直到…为止”，如：I will wait till（until）seven o#39;clock．till和until用在否定句中，均可表示“在…以前”或“直到…才”。

时间状语从句Before/After/Until/Since1、时间状语从句（二）由before和after引导的时间状语从句的区别用法▲before引导的从句不再用否定式的谓语，并且当before 引导的从句位于主句之后，有时译成“就，才”。

还要注意主句和从句之间的时间关系。

当主句用将来时，从句总是用现在时；如果before引导的从句谓语用的是过去时，则主句动词多用过去完成时，这样以便体现动作发生的先后。

如：It will be four days before they come back. （主将从现，一一对应）他们要过四天才能回来。

Einstein almost knocked me down before he saw me. （几乎同时发生）爱因斯坦几乎把我撞倒才看到我。

My father had left for Canada just before the letter arrived. （主过完从过）我父亲恰好在信到之前去加拿大了。

They hadnotbeen married four months before they were divorced.他们结婚还不到四个月就离婚了。

▲after表示主句动作发生在从句动作之后。

主句和从句的动作的时间关系正好与before引导的从句相反。

如：After you think it over, please let me know what you decide.你仔细考虑过以后，告诉我你是怎样决定的。

After we had finished the work, we went home.完成工作之后，我们回家了。

（从句用过去完成时，主句用一般过去时）（三）till或until引导的时间状语从句的区别till和until 一般情况下两者可以互换，但是在强调句型中多用until。

但要注意的是：①如果主句中的谓语动词是瞬时动词时，必须用否定形式；②如果主句中的谓语动词是延续性动词时，用肯定或否定形式都可以，但表达的意思不同。

before和ago都能表示在一段时间以前，但是二者的内涵和具体用法有明显的区别：1. before表示从过去或将来某一时间算起多少时间以前，由于与这一时间状语连用的行为先发生在过去或将来某一时刻之前，因此往往出现在过去完成时态或将来完成时态中。

例如：①I called him up last night，but his mother told me he had left for Wuhan two days before.②She said that she had married him five years before.2.如果不具体表明多少时间以前，before意为"从前；以前"，表示从现在开始追溯到过去一段时间，或者主句的谓语动词表示的是经常、反复发生的行为，以副词的形式置于句末，可以用在现在完成时态中。

例如：①I have never been to Beijing before.②Have you ever seen a tiger before?③I often go over the lessons that I have learned a few days before.注意：before前的时间状语如果是特定的，含义不一样。

试比较：He said he had arrived here a day before. (一天前)He said he had arrived here the day before. (前一天)3. ago指的是从现在起到过去时间的某一点的一段时间。

这个时间状语常与一般过去时态或过去进行时态连用。

例如：①I graduated from the college twenty years ago.②I was asked what I was doing a month ago.4. 表示在某一时间点或事件以前时，只能用before，不用ago。

It+be+时间+before/since/when/that句型辨析I since1. 翻译“It is/has been+时间段+since从句”(1)当从句谓语动词为非延续性动词时，表示这段时间从该动作开始时算起，即“自从做……以来已经多久了”。

(2)当从句谓语动词为延续性动词时，表示这段时间从动作结束时算起，即“自从不做……以来已经多久了”。

It is two years since he joined the army.他参军两年了。

(从参军那一刻算起)It is two years since he was a soldier.他退役两年了。

(从他不再是士兵算起)2. 时态主句为现在时（一般或完成），从句都是一般过去时。

主句为过去式（一般性都用was就够了），从句都是过去完成时II before1. 翻译It was/will be+时间段+before...过多长时间将发生某动作或事情；或过了多久发生了某事或动作。

It was three years before he finished the work.他花了三年才完成这项工作.It will be three years before he finishes the work.他得花三年才能完成这项工作. 2.It won't be/take long before...不久就会…It won't be long before he finishes the work.他不久就会完成这项工作.2. 时态主句为过去式（一般性都用was就够了），从句用过去时主句为将来时，从句用现在时（用一般现在时表示将来）III when1. 翻译It is + 时间点+ when…当发生什么的时候是什么时候…It was one o’clock when he came in .2. 时态主句是什么时态，从句就是什么时态3.常考与强调句的区别It was five o'clock when we arrived at the small mountain village.It was at five o'clock that we arrived at the small mountain village.强调句去掉it、be和that，余下的部分仍是一个完整的句子。

时间状语从句before 和since的用法before 和since的用法1.连词before表示“还未...就...；不到...就...；...才...；趁...还没...”Before they reached the station, the train had gone.他们(还没)到达火车站前，火车已经开走了。

We hadn’t run a mile before he felt tired.我们跑了还不到一英里他就累了。

Please write it down before you forget it.趁你现在没忘把它记下来。

2.before的句型：It will be +时间段+before从句，表示“多久之后才”。

It won't be long +before从句，表示“不久之后将...”It will be half a year before I come back.半年后我才回来。

(一般现在时表将来)It won’t be long before we meet again.不久后我们将再见面。

3.since的句型：It is/has been+时间段+since从句。

若从句的谓语为非延续性动词，表示“自从动作开始以来有多久了”；若从句的谓语为延续性动词，表示“自从动作结束/完成...有多久了”，常译为“自从不...有多久了”。

It is three years since the war broke out.战争爆发以来，有三年了。

It is twenty years since I've seen her. 我已经二十年没见她了。

五、every time, each time, next time, the first time, any time, all the time 的用法这些短语用来引导时间状语从句，表示“每当..；每次...；下次...”等。

易错点10 并列句和状语从句目录01 易错陷阱（2大陷阱）02 举一反三【易错点提醒一】并列句易混易错点【易错点提醒二】状语从句易混易错点03 易错题通关易错陷阱1：并列句易混易错点。

【分析】1. 逻辑关系和句式结构判断法；2. 连词词义需牢记。

【高考链接】1.（2023年新高考I卷）To eat one, you have to decide whether to bite a small hole in it first, releasing the stream and risking a spill (溢出), ________ to put the whole dumpling in your mouth, letting the hot soup explode on your tongue.【答案】or【详解】考查连词。

句意：吃小笼包的时候，你必须要决定是先咬一个小口流出汤汁，还是把整个小笼包放进嘴里，让热汤在舌头上爆炸。

whether...or... “是……还是……”，固定搭配，根据句意，故填or。

【规律总结】示原因的从属连词because连用。

“或者”为表示选择关系的连词，or还可译为“否则”，可用于句型：“祈使句＋or＋陈述句”。

both... and..., neither... nor..., not only...but also..., either...or..., not...but...特殊搭配解题。

作并列连词。

when表示“在那时，突然”；while表示“然而，而”，表对比或转折关系。

并列连词when常用于以下句型中：...was/were doing ...when ……正在做……突然……...was/were about to do ...when ... ……刚要做……突然……...was/were on the point of doing ...when ... ……刚要做……突然……...had just done ...when ... ……刚/一……就……I had just finished my homework when Tom came to me.我刚写完作业，Tom就来找我了。

since的用法主要有两点：一是表示“自从……以来”，二是表示“既然”之意。

但如果只了解词的含义，而不了解其用法，在使用时就会造成错误。

例如：I have not heard from him since I lived in Shanghai.不少人会望文生义，将该句译为：“自从我住在上海以来，就再也没有收到他的信了。

”而实际上这个句子的译文并非如此，那么正确的含义是什么呢？下面谈谈since作连词引导时间状语从句的用法。

一、若since引导的状语从句的谓语动词是终止性的过去时，则从句表示的时间是“从动作开始的那一时刻起”。

如：He has studied very hard since he came to our school.自从他来到我们学校，他学习就非常努力。

We have been missing them since they left here自从他们离开这里，我们就一直很想念他们。

这是最常见的一种用法，此处不再多述。

二、若since引导的状语从句的谓语动词是持续性动词或表示状态的动词的过去时时，则从句表示的时间是“从那持续动作或状态结束时算起”。

如：I haven’t heard any noise since I slept. Sleep 为持续性动词，sleep的动作结束时，即“醒来”时，这句应译为“我醒后还未听到任何声音”。

John is now with his parents in New York, it is already three years since he was a teacher约翰现在和父母一起住在纽约，他不当教师已经三年了。

本文开始出现的那个句子就可以译为“自从我离开上海，就再也没有收到他的信。

”这种译法常被人们误用，我们不妨再多举几个例子看看：How long is it since you lived in Shanghai?你离开（没住在）上海多久了？It is half a month since he was a League member.他退团（不当团员）半个月了。

since和before的用法时态
"Since" 和 "before" 都可以用于表示时间或事件的关系，但它们在句子中所表示的时间关系略有不同。

1. "Since" 在句子中表示自从某个时间点或事件之后一直持续到现在。

通常用于现在完成时或过去完成时等时间时态。

例子：
I have lived in this city since 2010. 我自2010年以来一直住在这个城市。

She had been working in the company since she graduated from college. 她自从大学毕业后一直在这家公司工作。

2. "Before" 在句子中表示在某个特定时间点或事件之前发生的动作。

通常用于过去时或过去完成时等时间时态。

例子：
He left the house before I arrived. 他在我到达之前离开了房子。

She had finished her homework before her parents came back. 她在父母回来之前已经完成了作业。

since和before引导的时间状语从句区别2014-08-31 08:53阅读：3,314since:since从句中的动词不同，其起算时间也不同。

' since+瞬间动词过去时' 是从该动作发生时起算；' since+延续性动词过去时' 是从该动作结束时起算。

试比较:He has worked very hard since he entered the factory.( enter为瞬间性动词，该句为: 从他入厂以来，他工作一直非常努力。

)We haven't seen each other since I worked in the factory.( work为延续性动词，该句为: 自从我不在工厂以来，我们没见过面。

可说成: We haven't wen each other since I stopped working in the factory.)since常用于“It' a+some time+since sb. did sth“结构。

试比较:It's two years since he joined the army.他参军有两年了。

It' a two years since be was a soldier.他退役有两年了。

before:before有时可译为“还没……就“。

【例】He had measured me beforer I could say a word.我还没来得及说话, 他就给我量好了尺寸。

I hadn't waited long before he came.我还没等多久他就来了。

I slipped out before the lecture started.还没等讲座开始我就溜了出去。

before也可用于it结构，与since 结构比较相似，注意它们所用时态的区别，其结构通常是:'It will be + some time + before sb. does sth.’或' It wa s + some time + before sb. did sth. '。

高考英语常考句式——it is +时间+ since (before, when)…请注意以下三个句式的区别和意思上的差异（其中的 is 根据情况可以有其他时态形式）：It is + 时间段 + since…的意思是“自从……以来有一段时间了”。

It is + 时间点 + when…的意思是“当……的时候时间是……”。

It is + 时间段 + before…的意思是“在……之前有一段时间”。

请看以下用例：It’s ten years since they got married. 他们结婚到现在已经十年了。

It was past one o’clock when he came in. 他回来时已经一点多了。

It won’t be long before they understand each other. 过不了多久他们就会互相了解的。

有时翻译可以比较灵活：It’s a long time since I met you last. 好久不见了。

(直译：自上次见到你以来有很长一段时间了。

)It’s about three years since I last played basketball. 我差不多有三年没有打篮球了。

(直译：自从我上次打篮球以来已差不多有三年了。

)请看有关高考题(答案为DDBCDC)：1.That was really a splendid evening. It’s years _________ I enjoyed myself so much. (安徽卷)A.whenB.thatC. beforeD.since2.It was some time _________we realized the truth. (山东卷)A.whenB.untilC.s inceD.before3.—Did Jack come back early last night?—Yes. It was not yet eight o’clock _________he arrived home. (福建卷)A.beforeB.whenC.thatD.until4.Scientists say it may be five or six years _________it is possible to test this medicine on human patients. (福建卷)A.sinceB.afterC. beforeD.when5.It was evening we reached the little town of Winchester. (天津卷)A.thatB.untilC.sinceD.before6.It _________ long before we _________ the result of the experiment. (上海春)A.will not be; will knowB.is; will knowC.will not be; knowD.is; know【全真模拟训练】1.It was about midnight _________ we found the lost child, crying under a tree.A.thatB.until C .when D.where2.It's some time _________ I have spoken to you about this matter.A.thatB.unlessC.si nceD.until3.It was ten _________ he stood at aunt’s door and rang the bell.A.whenB.untilC.sin ceD.that4.I think it won’t be long _________ they understand each other.A.whenB.untilC.sin ceD.before5.How pleased I am tonight! It’s years _________ we had so great a time together.A.whenB.thatC.be foreD.since6.It was some time _________ we realized how important the matter is.A.whenB.untilC.sin ceD.before7.—Did you come home very late last night?—No. It was just half past seven _________ I appeared before my parents.A.thatB.whenC.un tilD.since8.How time files! It seems like years _________ I last saw you.A.whenB.thatC.si nceD.before9.It’s more than half a century _________ the People’s Republic of China was liberated.A.whenB.thatC.si nceD.after答案：1—5 CCADD 6—9 DBCCwhen〔引导时间状语从句〕具体地说，它有以下几种含义：1．表明一个动作发生的时候，另一个动作正在进行之中。

Since\before\until的辨析练习：the soldier devoted most of his time to the security of the country. and it has been three years ____he went home .A. before B. after C. since D until,It has been two years___ I graduated from my high school.自从我高中毕业,已经两年了.It is still a year ___ I graduate from my college.在我大学毕业之前,仍然还有一年的时间.I had finished my homework ____ it was 9 o`clock last night. 在昨天晚上9点之前,我就已经完成了我的作业.I did not finish drawing the picture ____ it was 9 o`clock last night. 直到昨天晚上9点我才画完这幅画.since是自从的意思”一段时间+since”表示从这个时间开始到现在---自从~以来. 用法上It + ( 现在完成时) + 一段时间+ since + ( 一般过去时)例句：It is / has been four days since I caught a cold.我感冒已四天了It is / has been two weeks since we met last.自从我们上次见面以来已过了两周.一段时间+ before表示在这个时间之前,或者大约在这个时间上就会发生某事.用法上It + ( 一般将来时) + 一段时间+ before +( 一般现在时)例句：It will be five years before he meets you again. 五年之后他就会再见你的. It + be (not) + long before表示"(不)很久/ 才…"或"(没)过多久就/ …"It was (not) long before ….(谈论过去)\ It will(not) be long before ….(谈论将来)\ It was long before she came back.\没过多久她就回来了.\ It will be long before we meet again.\x0d很久以后我们才会再见面.\ It will not be long before we turn our hope into reality. 过不了多久我们的希望就会变成现实. 这里it指时间, before是连词,引导时间状语从句.long可用一段时间来替代.Until1. 如果（主）句中的谓语动词是终止性动词即非延续性动词,应采用“...not ...until ...”结构,意为“……到……时候才……”.例如：You mustn’t eat anything until you see the doctor.看过医生之后,你才能吃东西.Don’t get off the bus until it has stopped. 车停稳了以后再下车.2. 用于肯定句中：1) It may last until Friday.这可能要延续到星期五.2) He will be working until 5 o'clock.他将一直工作到五点钟.3) She was a bank clerk until the war, when she trained as anurse.她战前是个银行职员,战时受训当了护士.不难看出until 用于肯定句中,表示句子的动作一直持续到until短语所表示的时间为止,即表示动作的终点.一般可译为“直到……时(为止)”或“在……以前”.在这种用法中,句子的谓语动词必须是持续动词(非瞬间动词),如live, wait ,last, love, like, stay, work, continue等.3. 如果谓语动词为否定式,则until应译为“到……时候才”,即“在……以前不”.例如：I did not watch TV until she came back.（= I began to watch TVwhen/after she came back.）直到她回来我才开始看电视.4. 连词until引导的从句中谓语动词的时态.1）主句的谓语动词为一般现在时或一般将来时时,until从句中的谓语动词为现在完成时,用来强调从句谓语动词表示的动作发生在主句谓语动词表示的动作之前.试比较：I won’t go to bed until I have finis hed my homework.我要完成作业才睡觉.2）主句中的谓语动词为一般过去时时,从句中的谓语动词为过去完成时,用来强调从句谓语动词的动作发生在主句谓语动词表示的动作之前.试比较：Li Lei didn’t come until the film had begun.直到电影开演,李雷才来.〔特别提醒〕till和until的意思基本相同,用法也基本一样,但until 语气较重,多用于较正式的文体里.till多用于英式英语,until多用于美式英语；till不能用在句首,也不能用在not开头的短语或从句里,而until可以.例如：Until he came home, we knew the news.在他到家之前,我们不知道这消息.Not until nine o’clock yesterday evening did we finish the work. until和before用法的区别一、在下列情况下,两者可互换用,但含义略有不同.before表示“在……之前”的意思,强调时间先后关系；而until表示“直到……才”的意思,主句是肯定句则表示主句动作的终止时间；主句是否定句则强调主句动作的起始时间.1.主句为否定式终止性谓语动词.常见的动词是open, start, leave, arrive, finish, stop等.例如：(1)The noise of the street didn't stop until/before it was midnight.(2)The children won't come back until/before it is dark.(3)I didn't leave the lovely boy until/before his mother came home.2.主句为肯定式、延续性谓语词,这类动词用stand, stay, talk ,be, wait 等.例如：(1)He lived with his parents until/before he graduated from school.(2)I will wait until/before he comes to my help.(3)I shall stay here until/before you come back.二、在下列情况下,用before不用until.1.主句这肯定式、终止性谓语动词,只用before.“在…之前就”、“没来的及就”(1)He fell asleep before I could take off his clothes.(2)We arrived there before it started to rain.(3)The holiday came to the end before I knew it.(4)He almost knocked me down before he saw me.2.主句谓语动词强调动词的迟缓性,只用before,常伴有时间段状语或时间段暗示.例：(1)It was quite some time before he found the elephant at all.(2)We had walked a long way before we found some water.(3)We had sailed for two days before we saw the land.(4)The fire lasted about four hours before the firefighters could control it.(5)It was midnight before my brother came home.(6)It was three months before they met again.3.如果强调从句谓语动作未发生,就发生主句谓语动作,只用before.常译为“未及”,“不”或“不等……就”.例：(1)We can leave early in the morning before it gets too hot.(2)I must write it down before I forget it.(3)We do want to buy something now before prices go up.4.在某些特定句型中用before.例如：(1)It was not long before the whole country rose up.(2)It will probably not be long before they understand each other.三、下列情况一般区别用until.1.主句是持续性谓语动词时,肯定、否定都可以,但意义完全不同.肯定表动作终止,而否定表动作开始.例如：(1)We discussed the problem until/before he came back.我们一直讨论到他回来.(2)We didn't discuss the problem until he came back.我们一直等到他回来后才讨论问题.2.not…until句型尽管在某些情况下可与before互换用,但在强调句中一般仍用until.例如：(1)It was not until he told me that I knew it.(2)It was not until he finished his homework that he went home.。

高考英语常考句式——it is +时间 + since (before, when)…请注意以下三个句式的区别和意思上的差异（其中的 is 根据情况可以有其他时态形式）：It is + 时间段 + since…的意思是“自从……以来有一段时间了”。

It is + 时间点 + when…的意思是“当……的时候时间是……”。

It is + 时间段 + before…的意思是“在……之前有一段时间”。

请看以下用例：It’s ten years since they got married. 他们结婚到现在已经十年了。

It was past one o’clock when he came in. 他回来时已经一点多了。

It won’t be long before they understand each other. 过不了多久他们就会互相了解的。

有时翻译可以比较灵活：It’s a long time since I met you last. 好久不见了。

(直译：自上次见到你以来有很长一段时间了。

)It’s about three years since I last played basketball. 我差不多有三年没有打篮球了。

(直译：自从我上次打篮球以来已差不多有三年了。

)请看有关高考题(答案为DDBCDC)：1. That was really a splendid evening. It’s years _________ I enjoyed myself so much. (安徽卷)A. whenB. thatC. beforeD. since2. It was some time _________we realized the truth. (山东卷)A. whenB. untilC. sinceD. before3.—Did Jack come back early last night?—Yes. It was not yet eight o’clock _________he arrived home. (福建卷)A. beforeB. whenC. thatD. until4. Scientists say it may be five or six years _________it is possible to test this medicine on human patients. (福建卷)A. sinceB. afterC. beforeD. when5. It was evening we reached the little town of Winchester. (天津卷)A. thatB. untilC. sinceD.before6. It _________ long before we _________ the result of the experiment. (上海春)A. will not be; will knowB. is; will knowC. will not be; knowD. is; know【全真模拟训练】1. It was about midnight _________ we found the lost child, crying under a tree.A. thatB. untilC. whenD. where2. It's some time _________ I have spoken to you about this matter.A. thatB. unlessC. sinceD. until3. It was ten _________ he stood at aunt’s door and rang the bell.A. whenB. untilC. sinceD. that4. I think it won’t be long _________ they understand each other.A. whenB. untilC. sinceD. before5. How pleased I am tonight! It’s years _________ we had so great a time together.A. whenB. thatC. beforeD. since6. It was some time _________ we realized how important the matter is.A. whenB. untilC. sinceD. before7.—Did you come home very late last night?—No. It was just half past seven _________ I appeared before my parents.A. thatB. whenC. untilD. since8. How time files! It seems like years _________ I last saw you.A. whenB. thatC. sinceD. before9. It’s more than half a century _________ the People’s Republic of China was liberated.A. whenB. thatC. sinceD. after答案：1—5 CCADD 6—9 DBCCwhen〔引导时间状语从句〕具体地说，它有以下几种含义：1．表明一个动作发生的时候，另一个动作正在进行之中。

before和since引导的时间状语从句
"Before"和"since"在时间状语从句中都表示时间关系，但是他们的用法是不同的。

1."Before"表示在某个时间点或事件之前发生的事情。

例如：
（1）I will finish my homework before dinner. 我在晚餐前会完成作业。

（2）They usually eat breakfast before 7 o'clock. 他们通常在7点前吃
早餐。

2."Since"有两种用法，一种表示从过去某个时间点或事件开始，一直持续
到现在，另一种表示从过去某个时间点或事件开始，发生了另外一件事情。

例如：
（1）I have lived here since 2010. 我从2010年开始住在这里。

（2）It's been 10 years since I moved here. 我搬到这里已经10年了。

（3）We have not seen each other since last year. 我们从去年开始就没有见过面。

需要注意的是，当"since"引导的时间是时间点时，从句的动词用过去时态，如果是时间段，则用完成时态。

例如：
（1）I haven't seen him since last week. 自从上周以来，我一直没有见到他。

（2）We have not met since the beginning of the year. 自年初以来，我们没有见面过。

It+be+时间+before/since/when/that句型辨析I. since1.It is/has been+时间段+since sb did sth某个动作发生持续多久eg:It is/has been three years since he finished the work.自从他完成这项工作已经三年了.2.该句型中若since后跟延续性动词，要翻译成否定含义,即“没做某事已经多久了”.eg:It has been three years since he worked here.他不在这工作已经三年了.It has been three years since he smoked.他已经戒烟三年了.但是：It has been three years since he began to smoke.他吸烟有三年了。

II.before.1.It was/will be+时间段+before... 过多长时间将发生某动作或事情；或过了多久发生了某事或动作。

eg:It was three years before he finished the work.他花了三年才完成这项工作.It will be three years before he finishes the work.他得花三年才能完成这项工作.2.It won't be/take long before...不久就会…eg:It won't be long before he finishes the work.他不久就会完成这项工作.III when.when没有固定与It is…连用的句型.when可表示时间点或时间段，因此从句中短暂性动词或延续性动词均可用.when还可作并列连词，表示突然发生一个动作,等于and at that time.常用句型:1主语+was/were doing when...2主语+was/were about to do when...It+be+时间+before/since/when/that重要考点练习It +be+时间+before/since/when/that…是高考中每年必考的重要考点，而学生却对这个句型中几个关联词的选择把握不准，造成失分。