Unit3Languageinuse习题1.任务型读写Haveyoueverwonderedwhytherearesomanyskincoloursintheworld?Doyouknowwhypeoplelivinginparticularareasusuallyhaveacertaincolour?Biologyandhistoryarethetworeasonsforthis.Skincontainssomethingcalledmelanin,whichdeterminesaperson’sskincolour.Themoremelaninapersonhas,thedarkerhisorherskinwillbe.Theamountofandproductionofmelaninarecontrolledbygenetics,butcanbeaffectedbyotherthings,suchassunlight.Ifapersonlivesinaplacewithstrongsunlight,hisorherskinwillprotectitselfbyproducingmoremelanin,makingtheskindarker.Inaplacewithlesssunlight,aperson’sbodywillproducelessmelanin,makingtheskinlighter.Skincolourisalsoaffectedbyanothersource—vitaminD.HumansallneedvitaminDtobuildbones.Peoplecangetitbyeatingfoodssuchasfishandmilk,orfromsunlight,whichcausesvitaminproductionintheskin.Melaninprotectsskinbyabsorbingsunlight,sosunlightabsorbedbymelanincannotbeusedforvitaminDproduction.Therefore,adark-skinnedpersonwillproducelessvitaminDthanalight-skinnedpersonwhentheyreceivedthesameamountofsunlight.Evolutionhasgivenusarainbowofskincolours.Humanshavealwayshadmelanintodetermineourskincolour.Whathaschangedthroughhistoryistheenvironmentwherewehavelived.Thishasinturnchangedourmelaninproduction,andeventually,skincolour.Brief(1)▲Peoplelivinginaparticular(2)▲usuallyhavethesameskincolourandtherearemanydifferentskincoloursintheworld.ReasonsforskincolourThereasonsfordifferentskincoloursmainly(3)▲inbiologyandhistory.BiologicalreasonsTheamountofmelanin,bywhichaperson’sskincolouris(4)▲,variesfrompeopletopeople.Themoremelaninapersonhas,the(5)▲hisorherskinwillbe.VitaminDisanothersource(6)▲skincolour.VitaminDisnecessaryforhumanstobuildbones.SunlightcontributestovitaminDproductionintheskin.HistoricalreasonsTheearliestpeopleinAfricahaddarkskinwithhaircoveringitbecausethesunlightisverystrong..Whentheymovedtoplaceswheretheycouldnotgetenoughsunlightto(7)▲vitaminD,theirskincolourbecamelighter.Generallyspeaking,peopleinareaswithstrongsunlight,havedarkerskin(8)▲peopleinotherareashavelighterskin.(9)▲Melanin(10)▲animportantroleinourskincolour.Withourlivingenvironmentchanging,melaninproductionischanged,whichleadstothechangesinourskincolour.2.单项选择1.—WhereisMike?—Hehasgoneaway__________theweekend.A.onB.forC.inD.at2._________aboy,heusedtohelphisfatheronthefarm.A.BeingB.AsC.HewasD.Hisbeing3.________noneedforustodiscusstheproblemagainsinceithasbeensettled.A.IthasB.TherehasC.ItisD.Thereis4.Hisfailuremadehisfatherthinkhima___________boy.A.disappointB.disappointedC.disappointingD.disappointment5.ThisisthebestwayIcanthinkof__________theproblem.A.solveB.tosolveC.solvingD.solved6.Thedayswelookforwardto_______atlast.A.comingB.cameC.comesD.becoming
