Whenthetrafficlightsturnred,wewillstopdrivingacarorcros...
问题详情：Whenthetrafficlightsturnred,wewillstopdrivingacarorcrossingastreet.Whyisredusedfortrafficlightsinsteadofothercolors?Asweknow,scattering(散*)happenswhenlightgoesthroughtheair.Forthesamemedia(媒...