521.Before a traffic signal changes from green to red, it will first display yellow. Regarding the meaning of theyellow light, which of the following is correct?
(A) The yellow light means "caution," and vehicles shouldslow down but may continue through the intersection.
(B) The yellow light warns drivers and pedestriansthat the red light is about to appear and the right of way will be lost; vehicles that have already passedthe stop line should proceed quickly, while those that have not should stop and wait.
(C) The yellow lightis merely a transitional signal between red and green with no legal regulatory effect.