Grammar语法2020春A+单元指引Unit7一、时间状语从句1.when&while表示“当……时候”①when后接“瞬间性”动词，即do,did,bedoinge.g.IworkedforaforeigncountrywhenIwasinShanghai.②while后接“延续性”动词，即bedoinge.g.Thebellrangwhiletheteacherwasexplainingtheexperimenttothestudents.③Thebellrangwhile/whentheteacherwasexplainingtheexperimenttothestudents.=Whenthebellrang,theteacherwasexplainingtheexperimenttothestudents.2.since表示“从……开始”使用规则：主句用现在完成时，从句用一般过去时(有since的部分为从句)e.g.Ithasbeenalmost20yearssinceweweretogether.(主句为Ithasbeenalmost20years；从句为sinceweweretogether)3.until表示“直到”①Pleasewaitonthechairuntilyournameiscalled.②常用句型not…until表示“直到……才”e.g.Ididn’tgotobeduntilIfinishedmyhomework.4.assoonas表示“一……就……”使用规则：主将从现，即主句用一般将来时，从句用一般现在时(有assoonas的部分为从句)e.g.I’llgiveittoherassoonasshearriveshere.(主句为I’llgiveittoher；从句为assoonasshearriveshere.)5.before&after①before表示“在……之前”Youshouldfinishyourlessonsbeforeyougoouttoplay.②after表示“在……之后”Afteryoufinishyourlessons,youcangoouttoplay.二、条件状语从句1.if表示“如果”使用规则：主将从现，即主句用一般将来时，从句用一般现在时(有if的部分为从句)Willyoubeangryifyourstudentsdon’tobeytherulesinclass?(主句为Willyoubeangry；从句为ifyourstudentsdon’tobeytherulesinclass)2.unless使用规则：主将从现，即主句用一般将来时，从句用一般现在时(有unless的部分为从句)Itwillbeworseunlesswetakeactiontoprotecttheenvironment.(主句为Itwillbeworse；从句为unlesswetakeactiontoprotecttheenvironment)3.if…not=unlessIfwetakeactiontoprotecttheenvironment,itwillnotbeworse.Unlesswetakeactiontoprotecttheenvironment,itwillbeworse.三、让步状语从句1.aslongas表示“只要”使用规则：主将从现，即主句用一般将来时，从句用一般现在时(有aslongas的部分为从句)Aslongaswekeepplayingwell,we’llkeepwinninggames.(主句为we’llkeepwinninggames；从句为Aslongaswekeepplayingwell)2.although/though表示“虽然”Although/Thoughjeanswereinventedover100yearsago,they’r...
