12月大学英语四级真题附答案及听力原文

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1、考试吧(Exam8.com)-第一个极力推崇人性化服务的专业考试培训网站！提供历年试题，模拟试题，模拟盘，教程，专业课试题下载，考试培训等。每日更新!!!　　PartⅠWriting(30minutes)　　Directions:Forthispart,youareallowed30minutestowriteashortessayentitledTheDecreaseofPublicTransportationTicketFare.Youshouldwriteatleast120wordsfoll

2、owingtheoutlinegivenbelow:　　1.近来一些城市政府实施多项举措降低公共交通票价，大力发展公共交通;　　2.此措施带来的好处;　　3.作为市民应如何响应政府的号召。　　TheDecreaseofPublicTransportationTicketFare　　PartⅡReadingComprehension(SkimmingandScanning)(15minutes)　　Directions:Inthispart,youwillhave15minutestogooverth

3、epassagequicklyandanswerthequestionsonAnswerSheet1.　　Forquestions1-7,choosethebestanswerfromthefourchoicesmarkedA),B),C)andD).　　Forquestions8-10,completethesentenceswiththeinformationgiveninthepassage.　　TheDebateOverGeneticallyModifiedFoods　　Forthousan

4、dsofyearsfarmershaveusedaprocessofselectionandcrossbreedingtocontinuallyimprovethequalityofcrops.Traditionalbreedingmethodsareslow,requiringintensivelabor:whiletryingtogetadesirabletraitinabredspecies,undesirabletraitswillappearandfarmersmustcontinueth

5、eprocessoverandoveragainuntilalltheundesirablesarebredout.Incontrast,organismsacquireonespecificgeneorafewgenestogetherthroughgeneticmodification,withoutothertraitsincludedandwithinasinglegeneration.However,thistechnologytooisinherentlyunpredictableand

6、somescientistsbelieveitcanproducepotentiallydangerousresultsunlessbettertestingmethodsaredeveloped.Traditionalbreedingisbasedonsexualreproductionbetweenlikeorganisms.Thetransferredgenesaresimilartogenesinthecelltheyjoin.Theyareconveyedincompletegroupsa

7、ndinafixedsequencethatharmonizeswiththesequenceofgenesinthepartnercell.Incontrast,bioengineersisolateagenefromonetypeoforganismandcollectitrandomlyintotheDNAofadissimilarspecies,disruptingitsnaturalsequence.Oneofthemaindifferencesbetweenconventionaland

8、geneticallymodifiedcropsisthattheformerinvolvescrosseseitherwithinspeciesorbetweenverycloselyrelatedspecies.However,GMcropscanhavegenesfromcloselyrelatedspeciesorevenfrombacteriaandviruses.Benefits:onesideofthedebateEconomical?GMsupport