Imaginearoadcrossingwithoutthethree-waytrafficsignal.Ca...
問題詳情:Imaginearoadcrossingwithoutthethree-waytrafficsignal.Cars,trucks,schoolbuses,bicyclistsandstudentswalkingtoschoolwouldtrytorushthroughthecrossing61_______thesametime.Theirsafetywouldbeindanger...