原因状语从句

状语从句在复合句中作状语,其位置较灵活,可以在主句之前、之后或中间(放在句首时状语从句后面常用逗号,放在句末时状语从句前面往往不用逗号)。根据状语从句的含义,状语从句主要分为时间状语从句、地点状语从句、原因状语从句、目的状语从句、方式状语从句、结果状语从句、条件状语从句、让步状语从句等八种。掌握以上各种状语从句的关键在于把握其相应的引导词。以下是对时间状语从句的基本用法进行小结,希望可以帮助到同学们有一更深的理解。时间状语从句的引导词when, before, after, as, while, till/until, since,whenever时间状语从句的用法时间状语从句的引导词所表示的意思不尽相同,要注意把握不同的时间状语从句的引导词所表示的不同时间关系,以及它在具体句子中对应的对应时态、语态等问题。1. when、as、while引导的时间状语从句分析:(1) when引导时间状语从句时表示“当……的时候”,when既可以指时间段也可指时间点,从句中既可用延续性动词又可用非延续性动词,且动作既可和主句的动作同时发生又可在主句的动作之前或之后发生。注意体会如下例句:I’ll call you when I get there.我一到那里就给你打电话。// When the wind blows, all the doors rattle.只要风一吹,这门就吱嘎作响。// He stopped trying, when he might have succeeded next time.他不再试了,其实他可能下一次就成功。// When I came home my wife was cooking dinner.我回家时,妻子在做晚饭。如果when引导的时间状语从句的主语与主句主语相同,而从句的谓语又是be动词时,那么从句中的主语和be可以省略;当when引导的时间状语从句的主语与主句主语相同时,往往还可以用“when+分词”的形式替代该状语从句。例如:When (you are) in trouble, ask her for help.当你遭遇麻烦的时候去向她求助。// When I came into the room (=When coming into the room), I found him lying there asleep.当我进入房间的时候,我发现他躺在那儿睡着了。(2) while引导时间状语从句时表示“当……的时候”,它强调主句的动作与从句的动作同时持续地进行,用于这一用法时while引导的时间状语从句和主句中的谓语动词必须是延续性动词,或者主句的动作发生在从句动作的进行过程中,主句中的谓语动词通常是非延续性动词,例如:Study while you study; play while you play.该学习的时候就学习,该玩的时候就玩。// I met her while I was at school.当我在学校的时候我遇见了她。(3) as引导时间状语从句时表示“当……时,一边……一边……”,侧重表示两个动作同时发生(包括一个主语同时进行两个动作),或者一种动作随着另一种动作的变化而变化。例如:He jumps as he goes along.他边走边跳。// I slipped on the ice as I ran home.我跑回家时在冰上滑了一跤。// I saw him as he was getting off the bus.正当他下公共汽车时,我看见了他。// As the wind rose the noise increased.刮风的时候噪声增大。[考题1] I had just steeped out of the bathroom andwas busily dryingmyself with a towel ____ I heard the steps.A. while B. when C. since D. after[答案] B[解析]下划线处表示“正在这时,突然……”,四个选项中只有when可以表示此含义。[考题2] He was abouthalfway(中间/一半)through his meal ____ a familiar voice came to his ears.A. why B. where C. when D. while[答案] C[解析]下划线处表示“正在这时,突然……”,四个选项中只有when可以表示此含义。[考题3] We were swimming in the lake ____ suddenly the storm started.A. when B. while C. until D. before[答案] A[解析]题意为“当我们正在湖里游泳的时候突然暴风雨开始了”,表示主句的动作处于从句的动作突然发生时应采用when(while不适合用于这样的语境),when表示“当……的时候”受限制条件最少。[考题4] — I’m going to the post office.— ____ you’re there, can you get me some stamps?A. As B. While C. Because D. If[答案] B[解析]主句中“get me some stamps”的动作发生在时间状语从句“you’re there”的过程之中,因此应选while既然表示这一时间关系(属于while引导时间状语从句的两大基本用法之一)。因此B选项是最佳选项。注意:如果主句的动作发生于表示“;当……时”的时间状语从句中的动作的进行过程中,从句常用进行时。例如:The landlady suspected that someone must have broken into the house when/while/as she was watching TV show.女房东怀疑在她看电视时曾有人闯入屋里。// When/While/As Tom was reading, Jim was arrested.在汤姆看书的时候,吉姆被逮捕了。[考题5] I ____ along the street looking for a place to park when the accident ____.A. went; was occurring B. went; occurredC. was going; occurred D. was going; had occurred[答案] C[解析]根据题干句子含义,事故发生于当我沿街行驶、寻找停车之处的时候;从句的动作发生在主句动作的过程中。主句的谓语动词go表示非延续性的动作,可以持续进行,应选用过去进行时的形式,从句的谓语动词为非延续性动词,应以一般过去时的形式表结果。2. before和after引导的时间状语从句分析:before引导时间状语从句时表示主句的动作发生在从句动作之前,after引导时间状语从句时表示主句的动作发生在从句动作之后。例如:See me before you leave.在你离开之前来见我。// Before they drive any of the buses, they will have to pass a special test.在驾驶公共汽车之前,他们必须通过专门测验。// I saw them after I arrived.在我抵达之后,我见到了他们。// I found his pen after he has left.在他走后,我找到了他的笔。[考题6] He was told that it would be at least three more months ____ he could recover and return to work.A. when B. before C. since D. that[答案] B[解析]表示“他康复并返回工作岗位之前至少还需要三个月”,下划线处应选用before。[考题7] It was some time ____ we realized the truth.A. when B. until C. since D. before[答案] D[解析]题干意为:过了一段时间我们才意识到真相。下划线处应填入表示“在……之前”的连词。3. till和until引导的时间状语从句分析:till和until这两个词作连词和介词时的意义和用法相同,一般可以换用(放在句首时通常用until的形式,till在口语中更为常见)。till和until引导时间状语从句时跟主句里肯定形式或否定形式的、表示延续性动作的谓语动词连用表示“到……为止”,跟主句里否定形式的、表示非延续性动作的谓语动词连用表示“直到……才(开始)”,例如:Walk till you come to a white house.一直走到一座白房子为止。// 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。[考题8] It is difficult for us to learn a lesson in life ____ we’ve actually had that lesson.A. until B. after C. since D. when[答案] A[解析]题干的句子可以直译为:“在我们一生中,学到某个教训是困难的,直到我们真正经历了这个教训为止。”[考题9] A good storyteller must be able to hold his listeners’ curiosity ____ he reaches the end of the story.A. when B. unless C. after D. until[答案] D[解析]讲故事的人应该始终抓住听众的好奇心,本题应选用表示“到……为止”(跟主句里肯定形式的表延续性动作的谓语动词连用)的until表示这一时间关系。[考题10] I don’t really work here; I ____ until the new secretary arrives.A. just help out B. have just helped outC. am just helping out D. will just help out[答案] C[解析] “I don’t really work here”表明说话人只是临时前来帮忙,“until the new secretary arrives”表明说话人,工作到新秘书就任为止,本题应选用表示“到……为止”(跟主句里肯定形式的表延续性动作的谓语动词连用)的until表示这一时间关系。4. since引导的时间状语从句分析:since引导的时间状语从句表示“自从……以来”,其用法主要有两种:(1)现在完成时的主句+since引导的一般过去时态的时间状语从句。例如:He hasn’t been home since he graduated.他毕业后没回过家。// They have been friends ever since they were in grade school.他们从小学起就一直是好朋友。// What have you been doing since I last saw you?自我上次和你见面以后,你在做什么?(2) It be(主句中谓语用一般式和用完成式区别不大,后者更具强调意味)+表示一段时间的词汇+since引导的时间状语从句。例如:It is two years since I became a postgraduate student.我成为研究生已经有2年了。It was three years since we had been there.我们在那儿已呆了三年。注意:since做介词时也表示“自从……以来”,其具体用法有两种情况:(1) since+表示过去某个时间点的词汇(如具体的年、月、日期、钟点)。例如:They have been friends since childhood.他们从幼时起一直是好朋友。She’s been skiing since childhood.她从幼时起就开始滑雪。I have been there many times since the war.自那次战争以来,我曾去该地多次。(2) since+表示一段时间的词汇+ago。例如:I have been here since five months ago.五个月以来我一直在这里。[考题11] They ____ friends since they met in Shanghai.A. have made B. have become C. have been D. have turned[答案] C[解析]题干中的since表示“自从……以来”,主句中的谓语动词应该表示从他们在上海相遇至今的持续性的动作,因此下划线处应填入可以表示持续性状态的have been(其他选项中的made、become、turned所表示的动作都不能延续,意味着结果)。[考题12] — What was the party like?— Wonderful. It’s been 2 years ____ I enjoyed myself so much.A. after B. before C. when D. since[答案] D[解析] since表示“自从……以来”。