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ID:12043115
大小:54.50 KB
页数:15页
时间:2018-07-15
《新概念英语第四册第十七单元语法和句型(教学用)》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、新概念英语第四册第十七单元语法和句型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.Itoverranawho
2、lecontinent.Itcauseddevastationbyburrowingandbydevouringtheherbagewhichmighthavemaintainedmillionsofsheepandcattle.Scientistsdiscoveredthatthisparticularvarietyofrabbit(andapparentlynootheranimal)wassusceptibletoafatalvirusdisease,myxomatosis.Byinfectinganimalsandlettingthemlooseinthebu
3、rrows,localepidemicsofthisdiseasecouldbecreated.Lateritwasfoundthattherewasatypeofmosquitowhichactedasthecarrierofthisdiseaseandpasseditontotherabbits.Sowhiletherestoftheworldwastryingtogetridofmosquitoes,Australiawasencouragingthisone.Iteffectivelyspreadthediseasealloverthecontinentand
4、drastically15新概念英语第四册第十七单元语法和句型reducedtherabbitpopulation.Itlaterbecameapparentthatrabbitsweredevelopingadegreeofresistancetothisdisease,sothattherabbitpopulationwasunlikelytobecompletelyexterminated.Therewerehopes,however,thattheproblemoftherabbitwouldbecomemanageable.Ironically,Europe
5、,whichhadbequeathedtherabbitasapesttoAustraliaacquiredthisman-madediseaseasapestilence.AFrenchphysiciandecidedtogetridofthewildrabbitsonhisownestateandintroducedmyxomatosis.Itdidnot,however,remainwithintheconfinesofhisestate.ItspreadthroughFrancewherewildrabbitsarenotgenerallyregardedas
6、apestbutasasportandausefulfoodsupply,anditspreadtoBritainwherewildrabbitsareregardedasapestbutwheredomesticatedrabbits,equallysusceptibletothedisease,arethebasisofaprofitablefurindustry.ThequestionbecameoneofwhetherMancouldcontrolthediseasehehadinvented.【语法点】情态动词+完成体不定式15新概念英语第四册第十七单元语法
7、和句型【课文原句】Itcauseddevastationbyburrowingandbydevouringtheherbagewhichmighthavemaintainedmillionsofsheepandcattle.【闯关例句】1.havedonesthmusthavedonesthcanhavedonesthcouldhavedonesthmayhavedonesthmighthavedonesth2.presentstatuspositionmustbeateacher3.bedoingsthmustbewatchingTVpossibi
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