it is since,when,before用法

10.Itwas/willbe+时间段+before...该句型的is后可接long或一段时间。肯定句译为“过多久…才…”；过了多久将会。。。否定句译为“没多久…就…”。例如：ItwasalongtimebeforeIgottosleepagain.Itwillbehoursbeforehearriveshere.Itwasnotlongbeforehelefthishometown.Itwillbefiveyearsbeforewemeetagain.11．Itis…since…该句型表达“自从……以来已经多久了Itis15yearssincethewarended.Itisjustaweeksincewearrivedhere.Itistenyearssincehelefthishometown.Itmustbealmost5yearssincewelastmet.从句中可用现在完成时。例如：ItisthreeyearssinceI’veseenhim.=ItisthreeyearssinceIsawhim.since从句如为延续性动词，用一般过去时，表示“动作的结束”。例如：It’syearssinceIenjoyedmyselfsomuch.Itisfouryearssinceshewasanurse.HowlongisitsinceyouwereinLondon.12.Itis…when做。。。时间是该句型中when引导的是时间状语从句，其前面是表示时间的词作表语，强调句型中that前面被前调的是状语。例如：Itwasteno’clockintheeveningwhenhecameback.Itistwelveo'clockatmidnightwhentheyarrivedatalovelyvillage.Itwas2005whenhelefthishometown.9.----DidJackcomebackearlylastnight?----Yes.Itwasnotyeteighto’clock____hearrivedhome.A.beforeB.whenC.thatuntil10.Scientistssayitmaybefiveorsixyears____itispossibletotestthismedicineonhumanpatients.A.sinceB.afterC.beforeD.wh11.Hewastoldthatitwouldbeatleastthreemoremonths____hecouldrecoverandreturntowork.A.whenB.beforeC.sinceD.that12.Itwasevening____wereachedthelittletownofWinchester.A.thatB.untilC.sinceD.beforebcbc13.ThefieldresearchwilltakeJoanandPaulaboutfivemonths;itwillbealongtime____wemeetthemagain.A.afterB.beforeC.sinceD.when15.Thatwasreallyasplendidevening.Itisyears____Ienjoyedmyselfsomuch.A.whenB.thatC.beforeD.since16.Itwassometime____werealizedthetruth.A.whenB.untilC.sinceD.beforebdd•1,Itwastwoyears________herealizedthetruth2.Itis/hasbeentwoyears________helivedhere•3.Itwasmidnight________hearrivedhome.•4.Itwasatmidnight______hearrivedhome•5.Itwon'tbelong___hefinishesthework6.Ithasbeenthreeyears______heworkedhere•7,Ithasbeenthreeyears_____hesmokedbeforesincewhenwhenbeforesincesince过了两年他才意识到事实自她离开这已有两年了没多久他才能完成这项工作他不在这工作已有三年了