《大学英语(三)》作业

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1、大学英语（三）《大学英语（三）》作业PartI.ReadingComprehensionDirections:Therearethreepassagesinthispart.Eachpassageisfollowedbysomequestions.ForeachofthemtherearefourchoicesmarkedA,B,CandD.Youshoulddecideonthebestchoice.Passage1Inthesummerof1978anEnglishfarmernamedIa

2、nStevenswasdrivinghistractorthroughafieldofwheatwhenhediscoveredsomethingstrange.Someofhiswheatwaslyingflatontheground.Theflattened（被压平的）wheatformedacircleaboutsixmetersacross.Aroundthiscirclewerefoursmallercirclesofflattenedwheat.Inthefollowingyears

3、moreandmoresimilarcircleswerefoundinafieldofwheatorcorn.Sopeoplecannothelpbutaskthequestion:Whatcausesthecircles?Atfirst,peoplesuspectedthatthecircleswereatrick.Toprovethatthecircleswereatrick,peopletriedtocopythem:theytriedtomakecirclesexactlyliketh

4、eonesthefarmershadfound.Theycouldn'tdoit.Theycouldn'tenterafieldofgrainwithoutleavingtracks,andtheycouldn'tflattenthegrainwithoutbreakingit.Thecirclesareapparentlynotatrick.Manypeoplebelievethatbeingsfromouterspacearemakingthecircles.Somethinkthatthe

5、beingsaretryingtocommunicatewithusfromfarawayandthatthecirclesaremessagesfromthem.Othersbelievethatthebeingshaveactuallylandedonearthandthatthecirclesaremarksleftbytheirspaceships.Severaltimespeoplereportedseeingstrangeflyingobjectsnearfieldswherecir

6、cleslaterappeared.Scientistssaythey'renotsurewhatcausesthem.Theyhavesuggestedseveraltheories.Forexample,somescientistssaythat"microbursts"ofwindcreatedthecircles.Amicroburstisadownwardrushofcoolair—thesamedownwardrushofairthatsometimescausesanairplan

7、etocrash.Othersscientistssaythatforceswithintheearthcausethecirclestoappear.Butcirclesoftenappearinforms.Itishardtobelievethatanynaturalforcecouldcreatethoseforms.Andrecentlyfarmershavediscoverednotonlycirclesbutalsoothershapessuchastrianglesintheirf

8、ields.Couldanynaturalforcecreatedaperfecttriangleinafieldofgrain?Inthesummerof1990somescientistsspentthreeweeksinthepartofEnglandwheremanycircleshaveappeared.Theyhadallthelatesthigh-techequipment.Thisequipment—worth1.8milliondollars—recordednothing.B