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第PAGE\*MERGEFORMAT5页共NUMPAGES\*MERGEFORMAT5页 2021年12月大学英语六级考试听力原文(网络版) SectionB第二篇It'salwaysfuntowriteaboutresearchthatyoucanactuallytryoutforyourself.Trythis:TakeaphotoanduploadittoFacebook,thenafteradayorso,notewhattheURLlinktothepictureisandthendeleteit.Comebackamonthlaterandseeifthelinkworks.Chancesare:Itwill.Facebookisn'talonehere.ResearchersatCambridgeUniversityhavefoundthatnearlyhalfofthesocialnetworkingsitesdon'timmediatelydeletepictureswhenauserrequeststheyberemoved.Ingeneral,photo-centricwebsiteslikeFlickrwerefoundtobebetteratquicklyremovingdeletedphotosuponrequest.Whydo"deleted"photosstickaroundsolong?Theproblemrelatestothewaydataisstoredonlargewebsites:Whileyourpersonalcomputeronlykeepsonecopyofafile,large-scaleserviceslikeFacebookrelyonwhatarecalledcontentdeliverynetworkstomanagedataanddistribution.It'sacomplexsystemwhereindataiscopiedtomultipleintermediatedevices,usuallytospeedupaccesstofileswhenmillionsofpeoplearetryingtoaccesstheserviceatthesametime.Butbecausechangesaren'treflectedacrossthecontentdeliverynetworksimmediately,ghostcopiesoffilestendtolingerfordaysorweeks.InthecaseofFacebook,thecompanysaysdatamayhangarounduntiltheURLinquestionisreused,whichisusually"afterashortperiodoftime",thoughobviouslythattimecanvaryconsiderably.30Whatdoesthespeakeraskustotryout?31Whataccountsforthefailureofsomewebsitestoremovephotosimmediately?32WhenwilltheunwanteddataeventuallydisappearfromFacebookaccordingtothecompany?SectionB第三篇Enjoyinganicedcoffee?Betterskipdinnerorhitthegymafterwards,withacancercharitywarningthatsomeicedcoffeescontainasmanycaloriesasahotdinner.TheWorldCancerResearchFund(WCRF)conductedasurveyoficedcoffeessoldbysomepopularchainsinBritainincludingStarbucks,CaffeNeroandCostaCoffeetogaugethecaloriesasstudiesincreasinglylinkobesitywithcancer.Theworstoffender-acoffeefromStarbucks--had561calories.Othericedcoffeescontainedmorethan450caloriesandthemajorityhadanexcessof200.Healthexpertsadvisethattheaveragewomanshouldconsumeabout2,000caloriesaday
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