题目内容：
Questionsarebasedonthefollowingpassage．
Thepolarvortex(极地旋风)currentlysweepingacrosstheNorthAmericancontinentisbringingwiththescenesusuallyassociatedwiththeArcticorAntarctic.Massivesnowfallandviolentwindshavebroughttemperaturesdowntorecordlows.InsomeareasoftheUS,suchasthestateofIndiana,allbutessentialemergencyvehiclesarebannedfromtheroads.Peoplearebeingurgedtoremaininsideinthewarm.
Thehumanbodyisnotdesignedforpolarcold--mostofusliveintemperateandtropicalclimate,wherethemercuryrarelydipsbelowfreezing.Therearepopulationsthathaveadaptedtopolarextremes--liketheInuitinArcticCanadaandtribesliketheNenetsinthenorthofRussia--butthevastmajorityofHomosapiens(现代人)hasnoexperienceoflivinginsuchsub-zerotemperatures.AndwhileouringenuityandexpertisehasallowedustocreateclothingtowithstandallbutthemostviolentArcticblizzards,polarsurvivalisallaboutkeepingoutofthemostfearsomecoldunlessyouabsolutelyhaveto.
Whathappenswhenwegetcold?Thehumanbodyhasseveraldefencemechanismstotryandboostourcoretemperaturewhenitgetschilly.Ourmusclesshiverandteethchatter.Ourhairsriseandourfleshforms"goosebumps"---akindofevolutionaryechofromthetimeswhenourancestorswerecoveredinfur.Thehypothalamus(下丘脑),theglandinthebrainthatactsasyourbody'sthermostat(恒温器),stimulatesthesereactionstokeepthebody'svitalorganswarm,atleastuntilitcanfindsomekindofwarmthandshelter.
Thehypothalamus'smissionistokeepthecorewarmatallcosts--sacrificingtheextremitiesifneedbe.That'swhywefeelpinsandneedlesinourfingersandtoesinextremecold--thebodyiskeepingitswarmbloodclosetothecentre,constrictingbloodsupplyintheouterregionssuchastheendofourlimbs.Inextremecold,andespeciallyifbareskinisopentotheelements,thiseffectcanendinfrostbite.
Sohowdootherwarm-bloodedanimalslivinginsuchclimatecopewhenwecan't?Polaranimalsareeithercoveredinwintercoatsoffur---whichtrapswarmairclosetothebody--orelselargequantitiesoffat,sometimesinchesthick.Fatdoesnottransferheatverywell,soitkeepsitinsidethebody.Humans,withnakedskinandrelativelylittlefat,justaren'tbuiltfortheseenvironments.
Butwehavelearnedtoimitatethesequalities.ScientistsinAntarcticstations,forinstance,dressinlayersuponlayers,whichtrapswarmairclosetothebodylikefurdoes.
Whatcanwelearnfromthefirstparagraph? A．ThenorthareasoftheU.S.werestrickenbythepolarvortex.
B．ThetemperatureintheArctichasdroppedtorecordlow.
C．AllthevehiclesarebannedinsomeareasoftheU.S.
D．Thelocalgovernmentaskedpeopletostayinwarmplaces.
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