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When, before, since 句型1. when 的句型(1) be doing sth….when…正在做某事时…突然…We were swimming in the pool when it began to rain.We were studying English when he came in.(2) be about to do sth…. when …正要做…突然…We were about to leave when he came in.(3) had hardly/scarcely/just done sth…. when…刚…就…We had hardly finished the work when he came in.(4) when=now=since 表示“既然”It was foolish of you to take a taxi when you could get there in 5 mins. Now you are here, you’d better stay.2. before 句型(1) it will be + 时间段+ before sb. do sth. 再过多久…才…It was +时间段+before sb. did sth. 过了多久…才…It won’t be long before sb. do sth. 过不了多久某人就会…Eg. It will be 1 year before we go to college.It was 4 years before we graduated.(2) 主语+had done/did sth.+时间段+ before +did sth. 过了…才e.g. We had sailed for 4 days before we found the island.We waited a long time before the train arrived．我们等了很长时间火车才到。
状语从句知识点讲解定义：在句中作状语的从句叫状语从句，修饰主句中的谓语局部。
考点：状语从句有九种，其主要考点为各类连接词，理解句子即可。
一、时间状语从句(1) when/while/as1)when引导的时间状语从句意为“当・・•时候”，表示从句和主句的动作先后或者同时发生。
从句中的谓语动词可以用短暂性动词也可以用延续性动词。
例如：When the teacher came in, we were talking.When I first arrived on this country, I had nothing.2)While引导的时间状语从句意为“当…时候二表示从句和主句的动作同时发生。
从句中的谓语动词必须用延续性动词。
例如：I was sleeping while Tom was watching TV.3)as弓|导的时间状语从句意为“一边…一边”，强调主句和从句的动作同时发生。
例如：She sang as she worked.练一练：1.you came in, I was talking with a few boys.1.1t started to rain we were playing outdoors.3.They talked they walked down the river.4.it was raining, the students were playing basketball.5.Tom watched TV he ate supper.(2)before指主句的动作发生在从句的动作之前。
after指主句的动作发生在从句的动作之后。
例如：I'll be backbefore.你离开之前我就会回来。
What will you do after you graduate?你毕业之后想要干什么？(3)since引导的时间状语从句，从句的谓语动词通常为一般过去时，主句的谓语动词通常为现在完成时例如:He has been worried since the letter arrived.自从收到信,他就一直很担忧。
辨析before和since先看下面两道试题：1、What was the party like?Wonderful .It’s years I enjoyed myself so much. (NMET93)A.afterB.beforeC.whenD.since2、She was so interested in the book that she had read it for three bours she realized it.A.whenB.sunceC.beforeD.until在1题中，上下文提供人语言环境是：说话个方想询问另一方对晚会飞感受，另一方表达的一丝丝“晚会很精彩，自我上次玩得很开心以来已有好几年了。
”，时间的计算式从since从句飞完成或状态结束时算起。
因此应该选择D。
在2题中，上下文透露的语言信息是：在她意识到时间问题之前，时间已不知不觉飞过了三个小时。
也就是说三小时之后从句中的动作才开始。
答案应该选择C。
一、若表示“还未……就……”“不到……就……”“……才……”，“趁……还没来得及”是，需用连词before,此时从句中的谓语动词不能用否定时。
如We had sailed four days and four nights before we saw land.我们航行了四天四夜才看到陆地。
We hadn’t run a mile he felt tired.我们没跑到一英里，他就累了。
Please write it down before you get in a word, had measued me.我还没来得及插话，他就给我量好了尺寸。
Before they reached the station, the train had gone.他们(还没)到火车站之前，火车已开走了。
二、在“It+be+一段时间十before从句”句型中，如果主句为一般将来时，从句常用一般现在时；如果主句为一般过去时，从句则常用一般过去时。
夸克《英语语法大全》：since时间从句作名词后置修饰语语法在研究关系分句修饰时间的时候，只关心关系分句跟先行词在时间上的“重合”，而忽视了关系分句跟先行词不重合的情形。
譬如，在先行词之前的时间、之后的时间以及先行词所表示时间以来的范围，等等。
所以，一般语法书都涉及不到这些问题。
既然曹老师提出了这个问题，我也谈一下自己的看法。
when, since, before, after 这4个词，除了when 之外，其他三个既是介词，也是连词。
其共同特点是：这4个词引导的时间短语（不包括when，因为when 只引导从句）或从句，可以放在一个表示时间的名词之后作定语，现代语法只承认when 引导的从句是“关系分句”，其他情况均未涉及，也没有任何称谓或术语。
下面，我们分析这几个词引导从句作定语的用法，以及在表达时间上的不同：1. when 引导的关系分句，其谓语动词发生的时间，跟先行词的时间重合。
例如：I’ll never forget the day whe n I joined the Party.我决不会忘记入党的那一天。
【说明】先行词the day就是我入党的那一天。
“我忘不了的那一天”跟“我入党的那一天”重合。
2. since 把被修饰词的时间限制在since介词短语或从句发生以来的范围。
例如：Every hour since I came has been most enjoyable.我来之后的每一个小时都非常好玩。
【说明】Every hour 是句子主语。
since I came，无论从意思还是位置来看，都是作every hour 的定语。
如果是时间状语，它的位置要么在句首，要么在句末，不可能放在目前的这个位置。
since 把被修饰词every hour 的时间，限制在since 介词短语或从句发生以来的范围。
夸克认为被since 修饰后的句子，要含有“最高级”意义，是有道理的，因为since 表示一个“时间范围”，而主句表示在这个范围内，“有一个是最怎么样的”。
It+be+……+that/since/before/when用法辨析1.it was+ (时刻，或时间点）+ when sth. happened。
当某事发生时,是几点钟或哪一年如：It was 1997 when Hongkong returned to China。
It was five o’clock when we arrived at the small mountain village。
对比强调句型：It was at five o’clock that we arrived at the small mountain village。
It+ is/ was+…+that…多用于强调。
判断方法如下：去掉it、be和that，余下的部分仍是一个完整的句子,这样的句子一定是强调句。
2.it was+一段时间+ before sth happened。
过了一段时间之后,某事才发生了.如：it was two years before Macao returned to China.it will be +一段时间before sth。
happens.要过一段时间之后,某事才会发生。
或不用过多久，某些就将发生：it won't be long before sth。
happens。
It won’t be long before you see him again。
没过多久就…It was long before they escaped from the prison。
过了很久才….3。
it is (=has been)+一段时间since sth。
happened。
自某事发生以来,（时间）已经过去.。
了。
如：It is 11 years since Hongkong returned to China.香港回归已经有11年了。
若从句中的动词是终止性动词，意为：“从开始……多久了”例如：It has been five years since she left home.(她离家已经十五年了）It was four years since he had died.（到当时为止，他已死去四年了）若从句中的动词是延续性动词，意为：“不做某事已有多久了”例如：It is two days since she was ill.（她病好了两天)It is two years since he studied English。
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。
如何判断时间状语从句解析时间状语从句是指在主句中表示时间的从句，它可以用来说明事件发生的时间、持续的时间、频率等。
在英语中，时间状语从句通常由连词引导，如when, while, as, before, after, since, until, till, as soon as, once,等等。
那么如何判断时间状语从句呢？下面是一些判断时间状语从句的方法：1. 通过连词判断。
时间状语从句通常由when, while, as, before, after, since, until, till, as soon as, once等连词引导。
2. 通过时间状语从句的位置判断。
时间状语从句通常位于主句之前或之后，用来说明事件发生的时间、持续的时间、频率等。
3. 通过时间状语从句的语气判断。
时间状语从句通常使用陈述语气，表示客观的时间关系。
4. 通过时间状语从句的动词时态判断。
时间状语从句中的动词时态通常与主句中的动词时态相对应，用来表示时间的先后顺序。
5. 通过时间状语从句的语境判断。
时间状语从句的意义通常与主句的意义相关联，用来说明事件发生的时间、原因、结果等。
6. 通过时间状语从句的语法结构判断。
时间状语从句通常由一个完整的句子构成，包括主语、谓语和宾语等成分。
7. 通过时间状语从句的语调判断。
时间状语从句通常使用降调，表示客观的时间关系。
8. 通过时间状语从句的语义判断。
时间状语从句的意义通常与主句的意义相关联，用来说明事件发生的时间、原因、结果等。
9. 通过时间状语从句的逻辑关系判断。
时间状语从句通常与主句之间存在逻辑关系，用来说明事件发生的时间、原因、结果等。
10. 通过时间状语从句的语境和语义共同判断。
时间状语从句的意义通常与主句的意义相关联，用来说明事件发生的时间、原因、结果等，同时也需要考虑语境和语义的影响。
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。
