关于waytrafficsignalCa的百科

• Imaginearoadcrossingwithoutthethree-waytrafficsignal.Ca...

• 问题详情：Imaginearoadcrossingwithoutthethree-waytrafficsignal.Cars,trucks,schoolbuses,bicyclistsandstudentswalkingtoschoolwouldtrytorushthroughthecrossing61_______thesametime.Theirsafetywouldbeindanger.ThankstoanAfricanAmerican62________(invent)namedG...
• 2019-03-0316809