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1、Unit6GrammarIf--clausesif条件句表示的是事实时Oilfloatsifyoupouritonwater.Youmustseethedoctorifyouareill.在这种用法里，可用when代替if。if条件句谈论将来的情况IfIhaveenoughtime,Iwillcometoseeyou.Ifit'ssunnytomorrow,wewillgotohaveapicnic.Whatwillyoudoifyoufindapandaindanger?如果if条件从句放在句首，从
2、句后面用逗号。IfIcanaffordit,Iwillbuyavilla.Ifyoulike,youcanleavenow.若主句在前、if条件句在后，则主从句之间无须用逗号分开。IwillbuyavillaifIcanaffordit.Youcanleavenowifyoulike.一般情况下，if从句中的动词用一般现在时表示将来，主句动词则用将来时。Ifyougetherebeforeeight,wecancatchtheearlytrain.IfIhaveenoughtimenextweek,I
3、willcometoseeyou.有时if从句中的动词也可以用现在进行时或现在完成时。IfwearebuildingspaceshipsfortravellingtoMars,we'llhavetousesolarenergy.Ifyouhaven'tfinishedyourhomeworkby7:00,youcannotwatchthedramaonTV.if条件句不一般，几个要点记心间;条件句，放在前，逗号要放句中间。条件句表可能，主句多用将来时；条件句表事实，主句常用现在时。if后的从句可以有省
4、略形式在if引导的条件从句中，如果从句的主语是it，或与主句的主语相同，且在谓语中含有be动词时，常省略从句主语和be。If(itis)necessary,ringmeathome.If(itis)necessary,gotherebyair.Hewillcomeif(heis)asked.If(hewas)givenmoreattentionto,theboycouldhaveturnedoutbetter.祈使句和if条件句的转换“祈使句＋and＋简单句”结构可转换为含if条件状语从句的复合句。W
5、orkhard,andyou’lllearnwell．=If youworkhard,you’lllearnwell．“祈使句＋or＋简单句”结构可转换为含if条件状语从句的复合句，从句中的谓语须用其否定形式。Hurryup,orwe’llmisstheearlybus.=Ifwe don’thurryup,we’llmisstheearlybus.TranslatethesentencesintoEnglish.1.如果天气晴朗，他们要发射宇宙飞船。Iftheweather______,they_
6、_______thespaceship.isclearwilllaunch2.如果一颗人造卫星发生故障，宇航员要乘太空漫步去修复它。Ifasatellite________inspace,anastronaut_______________torepairit.isbrokenwilltakeaspacewalk3.如果你在太空，地球看上去是蓝色。Ifyou_________,Earth_______.areinspacelooksblue4.如果宇航员在月球行走，因为没有空气，他要穿着一件宇航服。I
7、fanastronaut______________,he_____________becausethereisnoair.walksontheMoonwearsaspacesuit5.如果宇航员想在月球上行走更远，他要开一辆月球车。Iftheastronaut____________________,he_______________.wantstotravelfarontheMoondrivesaMoonbuggy6.如果一切顺利，宇航员们会安全返回地球。goeswellIfeverything_
8、_________,theastronauts_________________.willlandsafelybackonEarthColumnAColumnB1.IfhespeaksEnglishwithaBritishaccent2.Ifyoulikeyellowroses3.Iftheunionworkersdon’tacceptthiscontract4.IfAmybuysablackdress5.IfMr.Edisontakesaplanea.
