Today,bicyclesareelegantlysimplemachinesthatarecommonar...
问题详情：Today,bicyclesareelegantlysimplemachinesthatarecommonaroundtheworld.Manypeopleridebicyclesforrecreation,whereasothersusethemasameansoftransportation.ThefirstbicyclewasinventedinGermanyin1818.B...