考点17阅读理解之说明文（2020•全国卷I，C）Racewalkingsharesmanyfitnessbenefitswithrunning,researchshows,whilemostlikelycontributingtofewerinjuries.Itdoes,however,haveitsownproblem.Racewalkersareconditionedathletes.ThelongesttrackandfieldeventattheSummerOlympicsisthe50-kilometerracewalk,whichisaboutfivemileslongerthanthemarathon.Butthesport’srulesrequirethataracewalker’skneesstaystraightthroughmostofthelegswingandonefootremainincontact(接触)withthegroundatalltimes.It’sthisstrangeformthatmakesracewalkingsuchanattractiveactivity,however,saysJaclynNorberg,anassistantprofessorofexercisescienceatSalemStateUniversityinSalem,Mass.Likerunning,racewalkingisphysicallydemanding,shesays,Accordingtomostcalculations,racewalkersmovingatapaceofsixmilesperhourwouldburnabout800calories(卡路里)perhour,whichisapproximatelytwiceasmanyastheywouldburnwalking,althoughfewerthanrunning,whichwouldprobablyburnabout1,000ormorecaloriesperhour.However,racewalkingdoesnotpoundthebodyasmuchasrunningdoes,Dr.Norbergsays.Accordingtoherresearch,runnershitthegroundwithasmuchasfourtimestheirbodyweightperstep,whileracewalkers,whodonotleavetheground,createonlyabout1.4timestheirbodyweightwitheachstep.Asaresult,shesays,someoftheinjuriesassociatedwithrunning,suchasrunner’sknee,areuncommonamongracewalkers.Butthesport’sstrangeformdoesplaceconsiderablestressontheanklesandhips,sopeoplewithahistoryofsuchinjuriesmightwanttobecautiousinadoptingthesport.Infact,anyonewishingtotryracewalkingshouldprobablyfirstconsultacoachorexperiencedracertolearnpropertechnique,shesays.Ittakessomepractice.28.Whyareracewalkersconditionedathletes?A.Theymustrunlongdistances.B.Theyarequalifiedforthemarathon.C.Theyhavetofollowspecialrules.D.Theyaregoodatswingingtheirlegs.29.Whatadvantagedoesracewalkinghaveoverrunning?A.It’smorepopularattheOlympics.B.It’slesschallengingphysically.C.It’smoreeffectiveinbodybuilding.D.It’slesslikelytocausekneeinjuries.30.WhatisDr.Norberg’ssuggestionforsomeonetryingracewalking?A.Gettingexperts’opinions.B.Havingamedicalcheckup.C.Hiringanexperiencedcoach.D.Doingregularexercises.31.Whichwordbestdescribestheauthor’sattitudetoracewalking?A.Skeptical.B.Objective.C.Tolerant.D.Conservative.A篇（2020•全国卷1D）Theconnectionbetweenpeopleandplantshaslongbeenthesubjectofscientificresearch.Recentstudieshavefoundpositiveeffects.AstudyconductedinYoungstown，Ohio，forexample,discoveredthatgreenerareasofthecityexperiencedlesscrime.Inanother，employeeswereshowntobe15%moreproductivewhentheirworkplacesweredecoratedwithhouseplants.TheengineersattheMassachusettsInstituteofTechnology(MIT)havetakenitastepfurtherchangingtheactualcompositionofplantsinordertogetthemtoperformdiverse，evenunusualfunctions.Theseincludeplantsthathavesensorsprintedontotheirleavestoshowwhenthey’reshortofwaterandaplantthatcandetectharmfulchemicalsingroundwater.＂We’rethinkingabouthowwecanengineerplantstoreplacefunctionsofthethingsthatweuseeveryday,＂explainedMichaelStrano,aprofessorofchemicalengineeringatMIT.Oneofhislatestprojectshasbeentomakeplantsgrow(发光)inexperimentsusingsomecommonvegetables.Strano’steamfoundthattheycouldcreateafaintlightforthree-and-a-halfhours.Thelight，aboutone-thousandthoftheamountneededtoreadby，isjustastart.Thetechnology,Stranosaid,couldonedaybeusedtolighttheroomsoreventoturntreeintoself-poweredstreetlamps.inthefuture，thet...
