假装不在上海
口语：Slow down on yellow / Slow down on a yellow light 语法无争议性而最简短的说法：Slow down when the light turns yellow.一般不需要说 traffic light 就能听得懂了。因为 turn red/green/yellow 的只有交通灯。不过若是考试，为了安全起见：Slow down when the traffic light turns yellow. 不是 turns to yellow.
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