Eachyearthereisanincreasingnumberofcarsonroadsandstreet...
問題詳情：Eachyearthereisanincreasingnumberofcarsonroadsandstreetsasmillionsofnewcarsandtrucksareproduced.OneoutofeverysixAmericansworksatputtingtogetherthepartsofcars,drivingtrucks,buildingroadsorfilli...