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1、八上Unit7Memory---GrammarConditionalsentences条件句If引导条件状语从句（1）If条件句：表示客观真理或客观事实，两个动词时态一致------一般现在时Ifyoutakeafishoutofwater（从句）,itdies（主句).Ifyoucoolsteam,itturnsintowater.If条件从句可以放在前面，也可以放在后面，放前面时，后面常用逗号隔开Ifyoucoolwater,itturnsintoice.Itturnsintoiceifyoucoolwater.（2）if条
2、件句：有可能性结果发生的行动，在这些句子中，动词的时态是不同的，if引导的条件状语从句中，主句用一般将来时态，从句用一般现在时态（主将从现）Ifitdoesn’train,we’llhaveapicnictomorrow.Ifwegobybus，itwillbecheaper.Ifyoudon'thurry,you’llmissthetrain．Ifthepictureissilly,strangeandcolourful,youwillrememberitbetter.IfIhavetime,Iamgoingtovisityo
3、u.Iwillgototheparkifitdoesn’traintomorrow(3)主祈从现（祈使句+if+一般现在时态）Putupyourhandsifyouhaveanyquestionstoask.Ifit'scoldlatertonight，takeyourcoatwithyou.Don'twaitformeifI'mlate.(4)主情从现（情态动词+if+一般现在时态）IfIgetthereearly,Icanseethedoctorquickly.ImaybuyacarifIpassmydrivingtest.
4、Ifyougotoanothercountry，youmustobeythelocallaws.注意：当主语是you时，if引导的条件状语从句=“祈使句+and/or+简单句”。and表示顺承，or表示转折，意为“否则”。Workhard,andyouwillmakegreatprogress.=Ifyouworkhard,youwillmakegreatprogress.Takecare,oryouwillfalloffthetree.=Ifyoudon’ttakecare,you’llfalloffthetree.Hurry
5、up,oryouwillbelate.=Ifyoudon’thurryup,youwillbelate.Unless引导条件状语从句unless:如果…不，除非，相当于if…not(助动词或be动词+not)Unlessyoulistencarefully（从句）,youwon’tknowtheanswer.（主句）=Ifyoudon’tlistencarefully（从句）,youwon’tknowtheanswer（主句）.=Youshouldlistencarefully,oryouwon’tknowtheanswer.I
6、can'tseeunlessIwearglasses.精选范本,供参考！=Ican'tseeifIdon'twearglasses.Unlessyoucanpayyourbills,you’llhavetoleave.=Ifyoucan'tpayyourbills,you’llhavetoleave.Youwillmissthebusunlessyouhurryup.You'llfailyourChemistrytestagainunlessyouworkharder.Youwillnevergetanywhereunlessy
7、ousetyourgoal．Unlessyouarefriendlytopeople,youwon'tgetonwellwiththem．（与人相处得好）口诀：条件句，放在前，逗号要放句中间，条件句，表可能，主将从现很简单，条件句，表事实，主从现在记心间。拓展延伸：1.If引导宾语从句，意为“是否”（if=whether）,从句用将来时态。Doyouknowifhewillcomeherethisafternoon?2.when,assoonas,not...until引导的时间状语从句也是用主将从现。典型例题1.—Idon’t
8、knowifhe______.—Hewillcomeifit______.A．comes;won’train B．willcome;doesn’trainC．comes;doesn'train D．willcome;won’train2
