![Trafficlightsarered,yellowandgreen.Theyareveryimportant...]( "Trafficlightsarered,yellowandgreen.Theyareveryimportant...")
- 问题详情：Trafficlightsarered,yellowandgreen.Theyareveryimportantsignals(信号).TrafficlightsareusuallyplacedatbusystreetcornerstohelpcontroltrafficSometimes,theyareonstreetsnearschoolsandshops,too.Mostyoungchildrenaretaughtwhateachofthecoloredlightsmea...
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