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1、Unit20Careanddiligencebringluck.谨慎和勤奋才能抓住机遇。学习内容题材词数建议时间得分统计做题备忘PartAText1科普知识380/10Text2商业经济425/10Text3社会生活475/10Text4文化教育457/10PartB商业经济713/10PartC科普知识415/10PartADirections：Readthefollowingtexts.Answerthequestionsbloweachtextbychoosing[A],[B],[C]or[D]
2、.Text1Withadvancingage,ourbodiesexperienceaninevitablelossofbone.Twomajorstudiesinelderlypopulationsnowunderscoretheimportanceofdietaryproteininthisstructuralerosion,whichcanleadtoosteoporosis.Thereportscometosharplydifferentconclusion,however,aboutthee
3、ffectofanimalproteinontherateofboneloss.Inonestudy,dietsrichinanimalproteincorrelatedwithgreaterbonelossandfracturerisk.Intheother,animalproteinappearedtoprotectbone.Suchcontradictions,“whicharenotverysatisfying”,oftenemergefromobservationalstudieswhere
4、researchersrecordthenaturalhabitsandhealthofpeople,notesRobertP.HeaneyofCreightonUniversityMedicalCenterinOmaha,Neb.“That’snotacriticismofsuchstudies,”hesays,“justareminderoftheuncontrollablevariablescommoninpopulations.”However,henotes,thenewstudiesare
5、importantbecausethey’reinthevanguardofeffortstounderstandprotein’simpactonage-relatedboneloss.ThisconditionunderliesagrowingU.S.epidemicofhipfractures.Treatingthemcostsmorethan$10billionannually.Thefirstofthenewanalysescomputedbonelossover7yearsinsome75
6、0elderlywomen,alltakingpartinalargerosteoporosisstudythat’sbeenrunningsince1986atfourU.S.sites.Womeneatingthemostanimalprotein—roughlyfourtimestheirvegetableproteinintake—lost0.8percentoftheboneintheirhipsannually,notesendocrinologistDeborahE.Sellmeyer,
7、directoroftheUniversityofCalifornia,SanFrancisco-MountZionOsteoporosisCenter.Thisisfourtimestherateofbonelossinparticipantswhoateaboutequalpartsanimalandvegetableprotein.Theriskofhipfracturesinwomeneatingthehighestproportionofanimalproteinwas3.7timestha
8、tinwomenregularlydowningequalquantitiesofanimalandvegetableprotein,theteamreportsintheJanuaryAmericaJournalofClinicalNutrition.Thefindingsmakesense,Sellmeyerargues,becausedigestionofanimalproteinreleaseslargeamountsofacidthatthek
