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1、PassageQuestions1to5arebasedonthefollowingpassage.Thefoodirradiationprocessisasimpleone.ThenewU.S.plant,VindicatorofFloridaIncorporatedinMulberry,Fla.,usesamaterialcalledcobalt60toirradiatefood.Cobalt60isradioactiveisotope(form)ofthemetallicelementcobalt.Cobalt60,which
2、givesoffradiationintheformofgammarays,isalsousedforradiationtherapyforcancerpatientsandforsterilizinghospitalequipment.Theradioactiveisotopeiscreatedbybombardingcobaltwithsubatomicparticlesinanuclearreactor.However,irradiationplantsdonotthemselvescontainnuclearreactors
3、.Intheirradiationplant,foodisexposedtothinrodsofcobalt60.Therodsgiveoffgammarays,whichdisruptchemicalprocessesincontaminatingorganisms.Thedisruptionbreaksdownthecellwallsoforganismsordestroystheirgeneticmaterial.Thedose,setbytheU.S.FoodandDrugAdministration(FDA),isenou
4、ghtokillorganismsonfood,butnotenoughtoproducesignificantchangesinthefooditself.Althoughirradiationslightlydecreasesthenutritivevalueoffoods,thelossislessthanthatproducedbysomeothermethodsoffoodpreservation.Canning,forexample,resultsinamuchgreaterlossofnutrients.Thosewh
5、oobjecttoirradiationsaythattheprocessmaycreatesubstancesnotfoundinnonirradiatedfood.Sincethe1960’sresearchershavestudiedirradiatedfoodatmicroscopiclevelstotrytofindsuchsubstances,calleduniqueradiolyticproducts.Afterreviewingthesestudies,theFDAdeterminedthatcompoundsfor
6、medduringirradiationaresimilartosubstancefoundinnonirradiatedfoodsandarenotdangeroustoconsume.Destructionofmicroorganismsthatcauseillnessisanimportantgoalofirradiation.About250millioncasesoffoodpoisoningor1perperson—occureveryyearintheU.S.,accordingtoFDAestimates.Foodp
7、oisoningcancausevomiting,diarrhea,fever,headache—and,occasionally,death.Becauseoftheapparentsafetyoffoodirradiation,andtheproblemspresentedbycontaminatedfood,scientificgroups—includingtheAmericanMedicalAssociation,theWorldHealthOrganization,andtheUnitedNationsfoodandAg
8、ricultureAssociation—havevoicednearlyuniversalsupportfortheprocess.Worldwide,38nationshaveapprovedirradiationfor355pr
