What color are school bus lights when preparing to stop?

Answer: B — Yellow

When a school bus is preparing to stop to pick up or drop off students, the lights will flash yellow. This warning signal alerts other drivers that the bus is about to make the stop and that they should prepare to either slow down or stop as well. The yellow lights serve as a cautionary measure, indicating to road users that they need to be alert for the bus's upcoming stop and any children who may be entering or exiting the bus. The function of the yellow lights is crucial for ensuring safety during school bus operations, as they provide a visual indicator that enhances the visibility of the bus's intentions. Other colors such as red are used once the bus has come to a complete stop to signal drivers that they must stop their vehicles, but the yellow lights specifically indicate the preparatory phase.