四级常考语法结构.doc

四级常考语法结构一、 动词的时态1．动词的时态可以下表表示：一般时态进行时态完成时态完成进行时态现在dodoesamare doingishasdonehavehasbeen doinghave过去didwasdoingwerehad donehad been doing将去shall dowillshallbe doingwillshallhave donewillshallhave been doingwill过去将来shoulddowouldshouldbe doingwouldshouldhave donewouldshouldhave been doingwould2.应注意事项（1）、在由if,unless,before,after,as soon as,when,once,until,however等引起的表时间和条件等状语从句中，主句用将来时，从句用现在时态表示将来时态 例：He’ll come to see you if he has time tomorrow.（2）、一些表示起始的动词，如begin,come,go,start,arrive,return,sail,end,stop,depart,open,close,be等，可用一般现在时表示按规定，计划或时刻表要发生的情况。

例：The store opens at 8:00 a.m. and closes at 9:00 p.m.（3）、一些表示起始的动词，如go,come,leave,start,arrive,stay,play,return,have,die等，可用进行时表示将来 例：I had just finished my work and was starting to take a bath.（4）、be going to, be to, be about to 也可表示将来 例：Great efforts to increase wheat production must be made if bread shortages are to be avoided.（5）、since 引起短语或从句时，句子或主名的谓语应用完成时（现在完成时、过去完成时），从句的谓语可用过去时和现在完成时只有在It has been(is)…since句型中，主句既可用完成时（has been）也可用现在时（is） 例：Ever since the Civil War, the status of women has been a live social issue in this country.（6）、由by引导的许多时间状语往往要求谓语部分为完成时态，如 by then, by now ,by the end of ,by the time that 等。

例：By the end of this month, we surely a satisfactory solution to the problem.A. have found B. will be finding C. will have found D. are finding 二、动词的语态1．英语动词的语态有两种，主动语态和被动语态主动语态是指句子中的主语是动作的执行者，而被动语态的主语是动作的承受者2．注意事项（1）、不及物动词没有被动语态2）、有些动词形式主动，意思被动 例：The play reads better than it acts.（3）、主语+need/require/want+doing有被动意义： 例：The watch requires mending.（4）、在hear,make,see,let,have,watch动词后的复合宾语中，不定式都不带to，但这种句子如果变为被动结构，to不能省略 例：They made him tell them everything.（主动）He was made to tell everything.（被动）（5）、有些系动词如get,become+分词的结构，意思也接近被动语态： 例：Many areas became liberated in the following months.（6）、带宾补的及物动词用于被动句时，补足语位于动词之后。

例：The children made the room beautiful.The room was made beautiful.三、虚拟语气1．在非真实条件中的虚拟语气条件从句谓语主句谓语与现在事实相反were/didwould(should,could,might)+动词原形与过去事实相反had+过去分词would(should,could,might)+have+过去分词与将来事实相反were to/shouldshould(would,could,might)+动词原形例：What would you do if you were in my place?2.条件从句中的if若省略，要把were,should,had等词提到主语前例：The business is risky.But should we succeed,we sould be rich.3.错综时间条件句条件从句中动作和主句动作发生的时间不一致时，动词的形式要根据表示的时间来调整例：If he were not so careless, he would not have confused salt with sugar.4. 有时假设的情况并不以条件从句表示出来，而是通过上下文或其他方式表现出来。

这时，也应注意非虚拟语气部份的动词时态例：He would have given you some help, but he has been so busy.5.其他形式的虚拟语气（1）、由wish引起的宾语从句当表示对现在和将来的愿望时，从句用过去式或用would/could/might+动词原形；当表示对过去的愿望时，从句用had+过去分词或could/would+完成式 例：I wish I could go with you, but I have to finish my report.（2）、would (had) rather表示与现在或未来事实相反的假设，从句动词用过去式；表示与过去事实相反的假设，从句动词用过去完成式 例：Betty would rather her boyfriend had come to New York yesterday.（3）、would (just) as soon, would sooner相当于would rather4）、had hoped后的从句表示过去未实现的愿望从句谓语动词用would+动词原形 例：Christina’s parents had hoped that she would become a doctor, but she wasn’t good at science.（5）、It is (high/about) time that …，从句中谓语动词常用过去式。

例：It’s already 5 o’clock now. Don’t you think it’s about time ? A. we are going home B. we go home C. we went home D. we can go home（6）、在advise, ask, suggest, demand, require, propose, request, command, order, recommend, insist, desire, urge, direct, maintain, move等表示愿望、建议和命令的动词后的宾语从句，谓语用should+动词原形，should也可省略 例：We desire that the tour leader us immediately of any change in plans. A. inform B. informs C. informed D. has informed（7）、在It is+ desired(demanded/ suggested/ required/ proposed/requested/ recommended/ ordered) that等结构后的主语从句中，谓语动词用should+动词原形，should也可以省略。

例：It is recommended that the project until all the preparations have been made. A. is not started B. will not be started C. not be started D. is not to be started（8）、在suggestion, proposal, advice, order, desire, demand, requirement, recommendation(推荐)，plan, decision, motion(提议), idea, resolution(决心)等表示建议、命令、愿望、决心等意思的名词后的表语从句和同位语从句中，谓语动词用should+动词原形，should也可省略 例：My suggestion is that we (should) send a few students to help the other groups.（9）、在某些形容词后的从句中，谓语动词也用should+动词原形，should也可省略。

这些形容词主要有necessary, important, essential, advisable, vital, urgent, incredible, desirable, imperative, strange, natural, better, appropriate, insistent, keen等 例：I don't think it advisable that Tim to the job since he has no experience. A. is assigned B. will be assigned C. be assigned D. has been assigned（10）、以as if, as though引起的从句中，谓语动词形式与（1）中wish后宾语从句中的谓语动词形式相同但在look, seem, sound, smell, taste, feel等动词后，as if(though)引起的从句可以表示真实条件句，不需要用虚拟语气 例：I remember the story as if I had just read it .（11）、以lest, for fear that, in case引起的虚拟从句中，谓语动词要用should+动词原形，s。