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复合句【语法要点】复合句是由一个主句加一个或几个从句所构成的句子。从句只用作句子的一个成分，不能独立。根据从句在句子中的作用，可分为名词性从句、定语从句和状语从句三类。（一）名词性从句名词性从句包括主语从句、表语从句、宾语从句、同位语从句。其关联词有连接词that、if、whether；疑问代词who、what、which和疑问副词when、where、how、why等。1.名词性从句句法结构：从属连词thatwhether主语从句Thathewillcomeiscertain.（that不可省）Whethersheiscomingornotdoesn’tmattertoomuch.（不能用if）宾语从句Ithink（that）hewillbeallrightinafewdays.Iwentinandaskedif（=whether）theyhadacheapsuit.Iwonderwhether（不能用if）itistrueornot.表语从句Thefactis（that）Ihaveneverbeenthere.Thequestioniswhether（不能用if）itisworthdoing.同位语从句Thefactthatshehadnotsaidanythingsurprisedallofus.Theyaskedmethequestionwhethertheworkwasworthdoing.连接代词thatwhowhomwhosewhich主语从句Whowillhelphimisnotknown.Whathesaidisveryimportant.Whichsidewillwinisnotclear.宾语从句（1）作及物动词的宾语。例如：Ireallydon’tknowwhatheisdoing.Doyouknowwho/whomtheyarewaitingfor?Heaskedwhosedictionaryitwas.Hecan’ttellwhichmethodtheywillusefortheexperiment.（2）作介词的宾语。例如：Payattentiontowhattheteachersaid.Iwonderedtowhomhehadgiventheletter.表语从句Thatiswhatheisworriedabout.Thequestioniswhowillcomehere.Thequestioniswhichteamwillwinthematch.连接副词wherewhenwhyhow主语从句Whereshehasgoneisnotknownyet.Whentheywillstartisnotknownyet.Whyhediditwasn’tquiteclear.Howhebecameagreatscientistisknowntousall.宾语从句Idon’tknowwherewearegoingtohavethemeeting.Pleasetellmewhenweshalldiscussourworkplan.Doyouknowwhyhesaidthat?WillyoutellmehowIcangettotherailwaystation?表语从句Thatiswherehewasborn.Thisiswhyheislate.Thisishowhedidit.Thequestioniswhenhewillbeback.同位语从句Ihavenoideawhenhewillcomeback.YouhavenoideahowworriedIwas.Theproblemiswherewecangetsomuchmoney.2.名词性从句的其它用法：1）if不能引导表语从句。连接代词who、what、whose、which不能引导同位语从句。2）有时as、asif/though、because也可以引导表语从句，能跟表语从句的谓语动词一般为系动词be、seem、look等。例如：Thingsarenotalwaysastheyseemtobe.事情并不总是像表面上看来的那样。Itlooksasifitweregoingtorain.Itisbecauseyoueattoomuch.3）介词宾语不可以用which来引导，而要用what来引导。例如：Wecanlearnwhatwedidnotknow.HewilltalktousaboutwhathesawintheU.S.4）连词that引导的名词性从句除能用在except、but、in后之外很少作介词的宾语，。其它一些介词的宾语从句如果由连词that引导，则需用it先行一步作形式宾语。例如：Heisagoodstudentexceptthatheiscareless.Youmaydependonitthattheywillsupportyou.5）若主句谓语动词是及物动词make、find、think、see、hear等，则把宾语从句置于宾语补足语之后，用it作形式宾语。例如：Wefinditnecessarythatwepractisespoken-Englisheveryday.6）某些作表语的形容词或过去分词后常接宾语从句，如sure、happy、glad、certain、pleased、afraid、surprised、satisfied等，连词that可省略，有的语法书称之为状语从句。例如：Iamsurethathewillsucceed.Iamafraidyoudon’tunderstandwhatIsaid.Motherwasverypleasedherdaughterhadpassedtheexams.7）连接代词whoever、whatever、whichever也可引导宾语从句。例如：Iwillshowyouwhateveryouwanttosee.Youmaychoosewhoeveryoulike.Iwilltakewhicheverfitsthesockets.（插座）8）同位语从句一般跟在某些表示抽象概念的名词后面，用以说明名词所表示的具体内容。常跟同位语从句的名词主要有：idea、news、fact、promise、answer、belief、condition、doubt、fear、hope、order、problem、proof、question、reply、report、suggestion、thought、truth等。由连词that引导同位语从句既无语法功能，也无词汇意义，只是引导词；由连词whether引导同位语从句无语法功能，但有词汇意义“是否”；由连词when、where、how引导同位语从句在句中分别作作时间、地点和方式状语。注意→①关联词只能用whether不能用if表示“是否”的情况如下：A)在表语从句和同位语从句中。例如：Thequestioniswhetherthefilmisworthseeing.Thenewswhetherourteamhaswonthematchisunknown.B)在主语从句中，只有it作形式主语时whether和if均可。否则，也只能用whether。例如：Whetherweshallattendthemeetinghasn’tbeendecidedyet.Ithasn’tbeendecidedwhether/ifweshallattendthemeeting.C)在介词之后（介词往往可以省略）。例如：Italldepends(on)whethertheywillsupportus.D)后面直接跟动词不定式时。例如：Hedoesn’tknowwhethertostayornot.E)与ornot连用时。例如：Wedidn’tknowwhetherornotshewasready.②关联词if、whether均可使用的情况如下：A)引导宾语从句，但当宾语从句是否定句时，一般用if引导。例如：Iwonderif/whetherthenewsistrueornot.Idon’tcareifitdoesn’train.B)在“be+形容词”之后。例如：Hewasnotsurewhether/ifitisrightorwrong.③用if引导宾语从句如果会引起歧义，应避免使用if而用whether。试比较：Pleaseletmeknowifyouwanttogo.Pleaseletmeknowwhetheryouwanttogo.（if从句既可理解为宾语从句，也可理解为条件状语从句）doubt作“怀疑”解接宾语从句时，主句为肯定句用whether或if，主句为否定句或疑问句用that。10）it作形式主语①that所引导的主语从句常由代词it作形式主语。且wh-系列引导词引导的从句均可。例如：Itmakeseveryonehappythatthegirlisstillalive.Itdoesn’tmattertoomuchwhetherhe’scomingornot.Itisstillopentoquestionwhoistoheadthegroup.谁领导这个小组还没定下来。②常以it作形式主语的句型有：—It+be+形容词(obvious、true、natural、surprising、good、wonderful、funny、possible、likely、certain、probable)+that从句—It+be+名词词组(nowonder、anhonour、agoodthing、apity、nosurprise)+that从句—It+be+过去分词(said、reported、thought、expected、decided、announced、arranged)+that从句—It+seem、happen等不及物动词及短语+that从句—It+doesn’tmatter(makesnodifference,etc)+连接代词或连接副词引导的主语从句—当that引导的主语从句出现在疑问句中时，也要以it作形式主语，而把主语从句后置。例如：Isittruethatthescientistwillgiveusalecturenextweek?（二）定语从句在复合句中修饰名词或代词的从句叫定语从句。被修饰的名词或代词叫先行词。引导定语从句的关系代词有who、whom、whose、which、that等和关系副词where、when、why等。关系代词和关系副词在定语从句中担任句子成分。而引导引导非限定性定语从句的关系代词有who、whom、whose、which、ofwhich等，这些关系代词都不能省略，通常不用关系代词that。例如：Ihavetwosisters,whoarebothstudents.关系词whowhichthatwhosewherewhen指代人物、地点等动物、物、地点等所有者地点时间例如：Thisisthemanwhohelpedme.Theyhaveadogwhosebarkingdrivesmemad.Iknowthereasonwhyhecamelate.Thisistheplacewherewelivedfor5years.IwillneverforgerthedaywhenImetMr.Liu.Thedoctorwhomyouarelookingforisintheroom.注意→先行词表示地点时，有时用where，有时用that引导定语从句。这时要根据从句的谓语动词是及物的还是不及物的，是及物的就用that(which),否则就用where。例如;Thisisthehousewherehelivedlastyear.Thisisthehousethat(which)hevisitedlastyear.关系代词which、who或that在限定性定语从句中作宾语时可省略。例如：Amsterdamistheplacewe