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Unit4Languagepoints1.because,as,since与forbecause表示原因的语气较强，回答why问句的提问。如果原因不重要，或为人所知，一般用as或since。for表示原因的语气较because弱，类似补充说明，一般不用来回答why提出的问题。引导的从句不能放在句首，而且前面一般用逗号与主句分开。Nooneknowsexactlyhowtheearthbegan,asithappenedsolongago.Whatitwastobecomewasuncertainuntilbetween4.5and3.8billionyearsagowhenthedustsettledintoasolidglobe.2.betodo表示可能性3.settleinto迁入settledown安定下来Theearthbecamesoviolentthatitwasnotclearwhethertheshapewouldlastornot.4.violentadj.猛烈的，激烈的,强暴的violence猛烈，暴力doviolenceto损害violently猛烈地Theywereintimetoproducecarbon,nitrogen,watervapourand…5.intimetodosth./forsth.来得及……Shewillbebackintimetopreparedinner.•intime及时终有一天•ontime准时•sometime一些时间•attimes时常•killtime消磨时间•behindtime落后•allthetime一直•atatime一次•atthistime这时•atthattime那时•atthesametime同时•innotime立刻•inthedaytime在白天•foralongtime长时间•atonetime同一时期，同时地•forthefirsttime第一次•fromtimetotime不时地•timeandagain反复地，不断地•haveagoodtime玩得高兴•intimeof在....的时候time的短语WaterhadalsoappearedonotherplanetlikeMarsbut,unlikeearth,ithaddisappearedlater.6.unlikeprep.与……不同；不像；非……的特征词语辨析：unlike，dislikeunlike(不像)是介词like(像)的反义词。dislike(不喜欢)是动词like(喜欢)的反义词。如：Aperson,unlikeamachine,isnotreplaceable.人和机器不同，是不可替代的。Hedislikesdogs.他不喜欢狗。Itwasnotimmediatelyobviousthatwaterwastobefundamentaltothedevelopmentoflife.7.本句中It只起形式主语的作用,真正的主语是thatwaterwastobefundamentaltothedevelopmentoflife.用It做形式主语是因为that引导的从句较长,如果按照正常语序来安排的话就显得头重脚轻了。如:Itisnowonderthathehaspassedtheexam.Whatmanyscientistsbelieveisthatthecontinuedpresenceofwaterallowedtheearthtodissolveharmfulgasesandacidsintotheoceansandseas.8.harmfuladj.有害的，伤害的harmv.&n.伤害harmfully伤害地harmless无害的harmlessly无害地beharmfulto对……有害doharmto对……有害dosb.harm对某人有害cometoharm受到损害cometonoharm未受到伤害Others,calledamphibians,wereabletoliveonlandaswellasinthewater.9.Othersothertheothertheothersanother10.aswellas…“(除...之外)也，又”,可连接并列的单词或短语Maryaswellasherparentslikestolistentomusic.Hegrowsflowersaswellasvegetables.aswell相当于too，一般放在句末。Heisaworker,andapoetaswell.aswellas相当于notonly…butalso，但两者在用法上有不同notonly…butalso侧重后者，aswellas则着重前者，即AaswellasB=notonlyBbutalsoA。Mr.Brownhasexperienceaswellasknowledge.（侧重前者，即experience）=Mr.Brownhasnotonlyknowledgebutalsoexperience.（着重后者，即butalso后面的部分）Theyproducedyounggenerallybylayingeggs.11.bydoing表方式、手段TheylearnEnglishbywatchingTV.12.lieliedliedlying说谎lielaylainlying躺；位于laylaidlaidlaying生蛋;产卵Whytheysuddenlydisappearedstillremainsamystery.12.remain在这里是系动词，意思是“保持；仍然是”Thustheyhave,intheirturn,becomethemostimportantanimalsontheplanet13.inone'sturn轮到某人inturn(三个以上)依顺序地，一个接一个地outofturn不依照顺序地taketurns轮流，依次，替换…,whichpreventsheatfromescapingfromtheearthintospace.14.阻止，制止:prevent…(from)doingsthstop...(from)doingsthkeep...fromdoingsth注意：在被动语态中，from不可省略。Asaresultofthis,manyscientistsbelievetheearthmaybecometoohottoliveon.15.asaresultof是短语介词，后跟名词、代词等，意为“由于…的原因”，相当于becauseof。Hewaslateasaresultoftheheavysnow.asaresult为副词用法，意为“结果是”，后面指事情的结果。Hegotupverylatetoday.Asaresult,hemissedthefirstbus.Sowhetherlifewillcontinueontheearthformillionsofyearstocomewilldependonwhetherthisproblemcanbesolved.16.dependonsb依赖某人取决于dependonsth取决于dependonsb/sthforsthtodosthdoingsth17．pulln．[C]&vt.拉(力)；拖；牵引力pullin进站停靠；pullon匆忙穿上(衣服)pullout离站；(使)摆脱困境pullthrough恢复健康；渡过危机18．cheerup感到高兴；感到振奋；(使)高兴起来cheersb.on(赛跑比赛中)以喝彩声鼓励某人；为某人加油cheerfuladj.快乐的；高兴的；兴高采烈的cheersint.(用于祝酒)干杯；再见；谢谢19．breakout突发；爆发breakin强行进入；打断breakthrough突破；冲破breakup破碎；解散；分手breakoff断开；中断；停顿breakawayfrom逃脱；脱离breakinto强行闯入；突然开始breakdown出故障；垮掉20．watchout密切注视；当心；提防=lookout,takecare,becareful。watchover照顾；监督；保护watchoutfor留意keepawatch守望；注视21．ButwhenItriedtostepforward,IfoundIwascarriedtwice_as_far_asontheearthandfellover.而当我试着向前迈步的时候，我发觉我被送出去很远，步子的跨度竟是在地球上的两倍，因而我摔倒了。twiceasfaras...意为“是……的两倍远”，属倍数表达法句型之一。倍数表达法：(1)倍数＋as＋形容词/副词原级＋as...①Thislineisthreetimesaslongasthatone.这根线是那根线的三倍长。(2)倍数＋形容词或副词比较级＋than...②Thishallisfivetimesbiggerthanourclassroom.这个大厅比我们的教室大五倍。(3)倍数＋thesize/height/weight/depth等名词＋of...③Theearthis49timesthesizeofthemoon.地球的体积是月球的四十九倍。(4)倍数＋asmany/much＋名词＋as...④Hehasgotthreetimesasmanybooksashissister.他的藏书量是他妹妹的三倍。22．“Oh，dear，”Icried，“walkingdoesneedabitofpracticenow_thatgravityhaschanged.”“天哪，”我大声说，“既然重力改变了，看来走路也的确需要练一练了。”nowthat“既然”，在意思和用法上同since，引导原因状语从句，口语中that可省略。