When should the red lights of a school bus be activated?

Answer: B — Prior to opening the door

The red lights of a school bus should be activated prior to opening the door to ensure the safety of students as they board or disembark from the bus. Activating the red lights serves as a warning to other drivers that the bus is in operation and that children may be entering or exiting, which heightens the alertness of surrounding traffic. This precaution is essential since children can be unpredictable and may not follow established safety protocols, so it's crucial that drivers understand they need to stop before the students approach the bus. In this context, activating the lights before opening the door provides a clear message that the bus is stopping and that the area around the bus is potentially hazardous. This proactive measure helps to protect children, giving them a safe environment to get on or off the bus, while also prompting approaching vehicles to come to a halt well in advance.