Asif(though)+主语+did/haddone…表示过去的情况用过去完成时，表示现在和将来的情况用过去时
Ourheadteachertreatsusasifwewereherownchildren，soallthestudentsinourclassthinkhighlyofher.
AlantalkedaboutRomeasifhehadbeenthere.
Alltoooften，peopletreatAIDSpatientsasiftheywerebadordangerous.
75.关系代词as，which的区别
(1).当定语从句是否定句或表示否定时只能用which.
Hecamehereverylate，whichwasunexpected.
(2).当as在从句中作主语是，后面常接动词的被动语态.如：beknown，besaid，bereported，beannounced.如从句的行为动词是主动语态，一般用which作主语.
Shehasbeenabsentagain，asisexpected.
Tomhasmaderapidprogress，whichmakesmeveryhappy.
(3).As常用在as(it)seemslikely，as(it)oftenhappens，as(it)wasprintedout，as(it)wassaidearlier，asIremember(it)，asIunderstand(it)，as(it)appears.等结构
Jackhaswonthefirstprize，asitoftenhappens.
ShehasreadwidelyinRomanticliterature，asitappearsfromheressay.
(4).As仍然保持作连词时常有的某种含义.
Davidistall，asaremybrothers.
Heopposedtheidea，ascouldbeexpected.
(5).当非限定性定语从句是一个复合结构时，只能用which
Bettyalwaystellalie，whichherparentsfindstrange.
76.关系副词where的用法；高考对where的考察驱于复杂，从先行词为明显的地点，转为地点模糊化.当先行词表示某人/物的situation，或某事物所发展的stage，或表示某事物的某方面时都可用where.
Eg.Theaccidenthadreachedapointwhereboththeirparentsaretobecalledin.
Wherewillallthistroublelead？
Thatiswhereyouaremistaken.
Youaresayingthateveryoneshouldbeequal，andthisiswhereIdisagree.
Icanthinkofmanycases，wherestudentsobviouslyknewalotofEnglishwordsandexpressionsbutcouldn’twriteagoodessay.
