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考研英语必背作文高分范文三年级的英语老师张利从今天起请病假1周,通知1,2班的同学。一班周一3,4节的英语课调到周3的5,6节;2班周二1,2节的英语课到周4的5,6节。请同学们按时上课,发通知者为教务处(DEAN‘SOFFICE)时间为3月30日NOTICEMsZhang,theEnglishteacherofGradethree,isleavingforaweekbecauseforsickness.Therefore,someadaptionhavetobemade.Herearenoticeforyou:Class1--classonMondaycourses3and4changetoWednesdayourses5and6.Class2--classonTuesdaycourses1and2changetoThursdaycourses5and6.Pleasepreparefortheclass.DEAN‘SOFFICE30thMar考研英语必背作文:TopazTopazisahard,transparentmineral.Itisacompoundofaluminum,silica,andfluorine.Gemtopazisvaluable.Jewelerscallthisvarietyofthestone"precioustopaz".Thebest-knownprecioustopazgemsrangeincolorfromrichyellowtolightbrownorpinkishred.Topazisoneofthehardestgemminerals.Inthemineraltableofhardness,ithasaratingof8,whichmeansthataknifecannotcutit,andthattopazwillscratchquartz.Thegoldenvarietyofprecioustopazisquiteuncommon.Mostoftheworld'stopaziswhiteorblue.Thewhiteandbluecrystalsoftopazarelarge,oftenweighingthousandsofcarats.Forthisreason,thevalueoftopazdoesnotdependsomuchonitssizeasitdoeswithdiamondsandmanyotherpreciousstones,wherethevalueincreasesaboutfourtimeswitheachdoublingofweight.Thevalueofatopazislargelydeterminedbyitsquality.Butcolorisalsoimportant:bluetopaz,forinstance,isoftenirradiatedtodeepenandimproveitscolor.Bluetopazisoftensoldasaquamarineandavarietyofbrownquartziswidelysoldastopaz.Thequartzismuchlessbrilliantandmoreplentifulthantruetopaz.Mostofitisvarietyofamethyst:thatheathasturnedbrown.NOTE:topaz/'tэupжz;`topжz/n(a)[U]transparentyellowmineral黄玉(矿物).(b)[C]semi-preciousgemcutfromthis黄玉;黄宝石.考研英语必背作文:Cohesion-tensionTheoryAtmosphericpressurecansupportacolumnofwaterupto10metershigh.Butplantscanmovewatermuchhigher;thesequoiatreecanpumpwatertoitsverytopmorethan100metersabovetheground.Untiltheendofthenineteenthcentury,themovementofwaterintreesandothertallplantswasamystery.Somebotanistshypothesizedthatthelivingcellsofplantsactedaspumps.Butmanyexperimentsdemonstratedthatthestemsofplantsinwhichallthecellsarekilledcanstillmovewatertoapprecia