B Itisnaturalthatchildrenarecuriousabouttheworldaroundthem.Forexample,theywanttoknowhowtheirheartsbeat.Theywanttoknowwhytheoceanwatertastessalty. Aschildrengrowup,theybecomecuriousaboutdifferentkindsofthings.Whentheyarebabies,theyareinterestedinthepartsoftheirbodiesandinthesmilesoftheirmothers.Theybecomeinterestedinthephysicalworldaroundthem:theplants,theanimals,thesky.Later,theybecomeinterestedinthethingsthatpeoplehavemade:wheels,bicycles,cars.Andwhentheyareadults,theircuriositycontinues.Sometimesthiscuriosityleadstoacareer(生涯、职业)inscience. Scientistsspendtheirlivestryingtofindoutabouttheworld.Thosewhoworkwiththeearthsciencesstudytheearth,theoceans,andtheskies.Otherscientistswhostudylivingthingsworkwiththebiologicalsciences.Athirdgroupofscientistsstudythephysicalsciences,e.g.physics,chemistry. Thesescientistshavealreadydiscoveredalotaboutourworld.Forexample,theytelluswhyyourheartbeatsfastwhenyourun.Theysaythatwhenyouarequiet,yourheartnormallybeatssixty-fiveorseventy-fivetimesaminute.Yourheartisapump(泵)thatpumpsbloodtoallpartsofthebody.Thebloodcarriesoxygenandnutrition.Whenyourun,yourmusclesworkveryhardandusethenutritionthatthebloodcarriestothem.Themusclesneedoxygen,too.Soyourbrainsendsasignaltotheheart.Thesignalmeansthatthemusclesneedmorenutritionandoxygen.Thentheheartbeatsfastandsendsbloodquicklytothemuscles.Itmaybeat90to140timesaminute. Ofcourse,scientistscannotanswerallofourquestions.Ifweask,“Whydoestheoceanwatertastesalty”scientistswillsaythatthesaltcomesfromrocks.Whenarockgetsveryhotorverycold,itcracks.Rainfallsintocracks.Therainthencarriesthesaltintotheearthandintotherivers.Theriverscarrythesaltintotheocean.Butthenweask,“Whathappenstothesaltintheocean?Theoceandoesnotgetsaltiereveryyear.”Scientistsarenotsureabouttheanswertothisquestion. Weknowalotaboutourworld,buttherearestillmanyanswersthatwedonothave,andwearecurious. 45.Accordingtothepassage,whichofthefollowingstatementsistrue? A.Peop 冯元琨回答:
45---48 DCAC
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