高中英语since从句when从句before从句的比较

“It+be+…+that/since/before/when从句”用法辨析•1.Itwas+(时刻，或时间点）+whensth.happened.当某事发生时，是几点钟或哪一年。如：•Itwas1997whenHongkongreturnedtoChina.•Itwasfiveo'clockwhenwearrivedatthesmallmountainvillage.•对比强调句型：Itwasatfiveo'clockthatwearrivedatthesmallmountainvillage.•It+is/was+…+that…多用于强调。•判断方法如下：去掉it、be和that，余下的部分仍是一个完整的句子，这样的句子一定是强调句。•2.Itwas/willbe+一段时间+beforesthhappened.过了一段时间之后，某事才发生了。•如：itwastwoyearsbeforeMacaoreturnedtoChina.•itwillbe+一段时间beforesth.happens.要过一段时间之后，某事才会发生。•或不用过多久，某些就将发生：itwon'tbelongbeforesth.happens.•Itwon’tbelongbeforeyouseehimagain.•没过多久就…•Itwaslongbeforetheyescapedfromtheprison.•过了很久才….•3.Itis(=hasbeen)+一段时间sincesth.happened.自某事发生以来，（时间）已经过去…了。•如：Itis11yearssinceHongkongreturnedtoChina.香港回归已经有11年了。•若从句中的动词是终止性动词，意为：“从开始……多久了”例如：•Ithasbeenfiveyearssinceshelefthome.（她离家已经十五年了）•Itwasfouryearssincehehaddied.（到当时为止，他已死去四年了）•若从句中的动词是延续性动词，意为：“不做某事已有多久了”例如：•Itistwodayssinceshewasill.（她病好了两天）•ItistwoyearssincehestudiedEnglish.（他已有两年没学英语了）•练习：请用before，since，that，when填空。•1.ItwaslastSunday_____IcameacrossMrBrown.•2.Itwasmidnight_____theyoungcouplecamebackfromtheball.•3.Itwon’tbeaminute_____thelunchisready.•4.Itistwoweeks_____theSmithslivedinourvillage.•5.Itwasnotuntil1920_____regularradiobroadcastsbegan.•6.WasitduringtheSecondWorldWar_____hedied?•7.Ithasbeenoneyear_____Igotthejob.•8.Itwasn’tlong_____theydrovetheenemyofftheircountry.•9.Itwillbetwoyears_____wemeetagain.•10.Itisyears_____Ienjoyedmyselfsomuch.thatwhenbeforesincethatthatsincebeforebeforesince•归纳：判断这些近似句型中究竟该用哪个连词的窍门是：先看时间是点还是段，是点就把when来填；是段再把时态看，was/willbe用before，is/hasbeen把since填；还有一点不能忘，去掉itbe和that，强调句式可还原。