Today,bicyclesareelegantlysimplemachinesthatarecommonar...
問題詳情：Today,bicyclesareelegantlysimplemachinesthatarecommonaroundtheworld.Manypeopleridebicyclesforrecreation,whereasothersusethemasameansoftransportation.ThefirstbicyclewasinventedinGermanyin1818.B...