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新概念英语第四册第十七单元语法和句型(教学用).doc


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新概念英语第四册第十七单元语法和句型(教学用).doc
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---------------------------------作者:_____________-----------------------------日期::_____________新概念英语第四册第十七单元语法和句型(教学用)新概念英语第四册第十七单元语法和句型Lesson17Aman-madedisease人为的疾病IntheearlydaysofthesettlementofAustralia,enterprisingsettlersunwiselyintroducedtheEuropeanrabbit.ThisrabbithadnonaturalenemiesintheAntipodes,sothatitmultipliedwiththatpromiscuousabandoncharacteristicofrabbits.Itoverranawholecontinent.Itcauseddevastationbyburrowingandbydevouringtheherbagewhichmighthavemaintainedmillionsofsheepandcattle.Scientistsdiscoveredthatthisparticularvarietyofrabbit(andapparentlynootheranimal)wassusceptibletoafatalvirusdisease,myxomatosis.Byinfectinganimalsandlettingthemlooseintheburrows,localepidemicsofthisdiseasecouldbecreated.Lateritwasfoundthattherewasatypeofmosquitowhichactedasthecarrierofthisdiseaseandpasseditontotherabbits.Sowhiletherestoftheworldwastryingtogetridofmosquitoes,Australiawasencouragingthisone.Iteffectivelyspreadthediseasealloverthecontinentanddrasticallyreducedtherabbitpopulation.Itlaterbecameapparentthatrabbitsweredevelopingadegreeofresistancetothisdisease,pletelyexterminated.Therewerehopes,however,emanageable.Ironically,Europe,whichhadbequeathedtherabbitasapesttoAustraliaacquiredthisman-madediseaseasapestilence.AFrenchphysiciandecidedtogetridofthewildrabbitsonhisownestateandintroducedmyxomatosis.Itdidnot,however,remainwithintheconfinesofhisestate.ItspreadthroughFrancewherewildrabbitsarenotgenerallyregardedasapestbutasasportandausefulfoodsupply,anditspreadtoBritainwherewildrabbitsareregardedasapestbutwheredomesticatedrabbits,equallysusceptibletothedisease,arethebasisofaprofitablefurindustry.ThequestionbecameoneofwhetherMancouldcontrolthediseasehehadinvented.【语法点】情态动词+完成体不定式【课文原句】Itcauseddevastationbyburrowingandbydevouringtheherbagewhichmighthavemaintainedmillionsofsheepandcattle.【闯关例句】1.havedonesthmusthavedonesthcanhavedonesthcouldhavedonesthmayhavedonesthmighthavedonesth2.presentstatuspositionmustbeateacher3.bedoingsthmustbewatchingTVpossibilityoughttohavedon
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