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专四阅读理解练习（一）thediscoveryoftheantarcticnotonlyprovedoneofthemostinterestingofallgeographicaladventures,butcreatedwhatmightbecalled“theheroicageofantarcticexploration”.bytheirtremendousheroism,mensuchasshakleton,scott,andamundsencausedanewcontinenttoemergefromtheshadows,andyetthatheroicage,littlemorethanacenturyold,isalreadypassing.modernscienceandinventionsarerevolutionizingtheendurance,futurejourneysintotheseicywasteswillprobablydependonmotorvehiclesequippedwithcaterpillartractionratherthanonthedogsthatearlierdiscoverersfoundsoinvaluableandhardlycomparable.fewrealizethatthisantarcticcontinentisalmostequalinsizetosouthamerica,andenormousfieldofworkawaitsgeographersandprospectors.thecoastsofthiscontinentremaintobeaccuratelycharted,andthemapingofthewholeoftheinteriorpresentsaformidabletasktothecartographerswhoundertakethework.oncetheirlaborsarecompleted,itwillbepossibletoprospectthevastnaturalresourceswhichscientistsbelievewillfurnishoneofthelargesttreasurehoardsofmetalsandmineralstheworldhasyetknown,andalmostinexhaustiblesourcesofcopper,coal,uranium,andmanyotheroreswillbecomeavailabletoman.suchdiscoverieswillusherinaneraofpracticalexploitationoftheantarcticwastes.thepolardarknesswhichhidesthiscontinentforthesixwintermonthswillbedefeatedbyhugebatteriesoflight,andmakepossibletheestablishingofair-fieldsforthefutureinter-continentalairservicesbymakingtheseareasaslightasday.presentflyingrouteswillbecompletelychanged,fortheantarcticrefuelingbaseswillmakeflightsfromaustraliatosouthamericacomparativelyeasyoverthe5,000milesjourney.theclimateisnotlikelytoofferaninsuperableproblem,fortheexploreradmiralbyrdhasshownthattheclimateispossibleevenformencompletelyuntrainedforexpeditionsintothosefrozenwastes.someofhispartiesweremenwhohadneverseensnowbefore,andyetherecordsthattheysurvivedtherigorsoftheantarcticclimatecomfortably,sothat,providedthattheappropriateinstallationsaremade,wemayassumethathumanbeingsfromallcountriescouldlivetheresafely.byrdevenaffirmsthatitisprobablythemosthealthyclimateintheworld,fortheintensecoldofthousandsofyearshassterilizethiscontinent,andrendereditabsolutelygermfree,withtheconsequencesthatordinaryandextraordinarysicknessanddiseasesfromwhichmansuffersinotherzoneswithdifferentclimatesarehereutterlyunknown.thereexistnoproblemsofconservationandpreservationoffoodsupplies,forthelatterkeepindefinitelywithoutanysignsofdeterioration;itmayevenbethatlatergenerationswillcometoregardtheantarcticasthenaturalstorehouseforthewholeworld.plansarealreadyonfoottosetuppermanentbasesontheshoresofthiscontinent,andwhatsofewyearsagowasregardedasa“deadcontinent”nowpromisestobeamostactivecenterofhumanlifeandendeavor.1.whendidmanbegintoexploretheantarctica.about100yearsago.b.inthiscentury.c.atthebeginningofthe19thcentury.d.in1798.2.whatmusttheexplorersbe,eventhoughtheyhavemodernequipmentandtechniquesa.braveandtoughb.stubbornandarrogant.c.well-likedandhumorous.d.stoutandsmart.3.themosthealthyclimateintheworldis___.a.insouthamerica.b.inthearcticregion.c.intheantarcticcontinent.d.intheatlanticocean.4.whatkindofmetalsandmineralscanwefindintheantarctica.magnetite,coalandores.b.copper,coalanduranium.c.silver,naturalgasanduranium.d.aluminum,copperandnaturalgas.5.whatisplannedforthecontinenta.buildingdamsalongthecoasts.b.settingupseveralsummerresortsalongthecoasts.c.mappingthecoastandwholeterritory.d.settinguppermanentbasesonthecoasts.（二）withoutregularsuppliesofsomehormonesourcapacitytobehavewouldbeseriouslyimpaired;withoutotherswewouldsoondie.tinyamountsofsomehormonescanmodifymoodsandactions,ourinclinationtoeatordrink,ouraggressivenessorsubmissiveness,andourreproductiveandparentalbehavior.andhormonesdomorethaninfluenceadultbehavior;earlyinlifetheyhelptodeterminethedevelopmentofbodilyformandmayevendetermineanindividual’sbehavioralcapacities.laterinlifethechangingoutputsofsomeendocrineglandsandthebody’schangingsensitivitytosomehormonesareessentialaspectsofthephenomenaofaging.communicationwithinthebodyandtheconsequentintegrationofbehaviorwereconsideredtheexclusiveprovinceofthenervoussystemuptothebeginningofthepresentcentury.theemergenceofendocrinologyasaseparatedisciplinecanprobablybetracedtotheexperimentsofbaylissandstarlingonthehormonesecretion.thissubstanceissecretedfromcellsintheintestinalwallswhenfoodentersthestomach;ittravelsthroughthebloodstreamandstimulatesthepancreastoliberatepancreaticjuice,whichaidsindigestion.byshowingthatspecialcellssecretchemicalagentsthatareconveyedbythebloodstreamandregulatedistanttargetorgansortissues.baylissandstarlingdemonstratedthatchemicalintegrationcouldoccurwithoutparticipationofthenervoussystem.theterm“hormone”wasfirstusedwithreferencetosecretion.starlingderivedthetermfromthegreekhormone,meaning“toexciteorsetinmotion.theterm“endocrine”wasintroducedshortlythereafter“endocrine”isusedtorefertoglandsthatsecretproductsintothebloodstream.theterm“endocrine”contrastswith“exocrine”,whichisappliedtoglandsthatsecrettheirproductsthoughductstothesiteofaction.examplesofexocrineglandsarethetearglands,thesweatgl