Withouttransportation,therecouldbenotrade.Withouttrade,therecouldbenotownsandcities.Townsandcities aretraditionallythe___16___ofcivilization.Therefore,transportationhelpsmakecivilization___17___. Throughoutmostoftheprehistoricperiod,peoplelivedbyhunting,fishing,and___18___wildplants.They hadnobeastsofburden,wheeledvehicles,orroads.Peopletraveled___19___andcarriedtheirinfantsand belongingsstrappedtotheirbacksorheads.Loadstooheavyforonepersontocarrywerestrappedtoapoleandcarriedbytwopeople. ___20___,peoplelearnedthattheycoulddragloadsalongthegroundonsledges.Duringlateprehistoric times,peoplebegantobuildsledgeswithrunners. Whenpeopledevelopedagricultureandbegantoestablish___21___settlements,tradebetweensettlements startedtodevelop,whichcreatedaneedforbetter___22___oftransportation.Thedonkeyandtheox,whichhad beentamedforfoodproductsandfarmwork,helped___23___thisneed.Theuseofdonkeysandoxenasbeastsof burdenenabledpeopleto___24___heavierloadsthantheycouldbefore. Peoplealsobegantodevelopwatertransportationduringprehistorictimes.Theybuiltraftsofsuch__25____aslogs orreeds.Later,peoplelearned___26___tomakedugoutsandcanoes.Peoplepaddledtheseearlycraftwiththeirhands orpropelledthemwithpaddlesor__27____. Thewheelwasinventedabout3500B.C.andsailboatabout3200B.C.Wheeledvehiclesandsailingvessels___28___transportation.Butthespeedoftransportationimprovedonly___29___overthecenturies.Inventorsproducedthefirstengine-___30___vehiclesduringthelate1700’sandtheearly1800’s.This developmentmarkedthebeginningofarevolutionintransportationthathascontinuedtothepresent. 16.A.highlightsB.pinpointsC.headquartersD.centers 17.A.possibleB.acceptableC.practicalD.typical 18.A.growingB.gatheringC.wateringD.moving 19.A.inturnB.ateaseC.onfootD.forfun 20.A.AllthewhileB.ForawhileC.IntimeD.Ontime 21.A.temporaryB.permanentC.regularD.steady 22A.knowledgeB.judgmentC.standardsD.means 23.A.recognizeB.developC.meetD.reduce 24.A.bearB.moveC.shareD.lift 25.A.materialsB.stylesC.itemsD.types 26.A.whereB.whenC.howD.as 27.A.polesB.sailsC.currentsD.winds 28.A.demonstratedB.revolutionizedC.witnessedD.initiated 29.A.considerablyB.continuouslyC.swiftlyD.slightly 30.A.poweredB.controlledC.orientedD.related