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ID:12143344
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时间:2018-07-15
《2012年12月大学英语四级真题 附答案及听力原文 》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
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.Youshouldwriteatleast120wordsfollowingtheoutlinegivenbelow: 1.近来一些城市政府实施多项举措降低公共
2、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,youwillhave15minutestogooverthepassagequicklyandanswerthequestionsonAnswerSheet1. Forquestions1-7,choosethebestanswerfromthef
3、ourchoicesmarkedA),B),C)andD). Forquestions8-10,completethesentenceswiththeinformationgiveninthepassage. TheDebateOverGeneticallyModifiedFoods Forthousandsofyearsfarmershaveusedaprocessofselectionandcrossbreedingtocontinuallyimprovethequalityofcrops.Traditionalbreedingmethodsareslow,requiringinte
4、nsivelabor:whiletryingtogetadesirabletraitinabredspecies,undesirabletraitswillappearandfarmersmustcontinuetheprocessoverandoveragainuntilalltheundesirablesarebredout.Incontrast,organismsacquireonespecificgeneorafewgenestogetherthroughgeneticmodification,withoutothertraitsincludedandwithinasinglegene
5、ration.However,thistechnologytooisinherentlyunpredictableandsomescientistsbelieveitcanproducepotentiallydangerousresultsunlessbettertestingmethodsaredeveloped.Traditionalbreedingisbasedonsexualreproductionbetweenlikeorganisms.Thetransferredgenesaresimilartogenesinthecelltheyjoin.Theyareconveyedincom
6、pletegroupsandinafixedsequencethatharmonizeswiththesequenceofgenesinthepartnercell.Incontrast,bioengineersisolateagenefromonetypeoforganismandcollectitrandomlyintotheDNAofadissimilarspecies,disruptingitsnaturalsequence.Oneofthemaindifferencesbetweenconventionalandgeneticallymodifiedcropsisthatthefor
7、merinvolvescrosseseitherwithinspeciesorbetweenverycloselyrelatedspecies.However,GMcropscanhavegenesfromcloselyrelatedspeciesorevenfrombacteriaandviruses.Benefits:onesideofthedebateEconomical?GMsupport
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