Eachyearthereisanincreasingnumberofcarsonroadsandstreet...
问题详情：Eachyearthereisanincreasingnumberofcarsonroadsandstreetsasmillionsofnewcarsandtrucksareproduced.OneoutofeverysixAmericansworksatputtingtogetherthepartsofcars,drivingtrucks,buildingroadsorfilli...