When are you allowed to proceed while a school bus is unloading children?

Answer: C — After the stop sign arm is retracted

The correct choice emphasizes the importance of safety regulations governing interactions with school buses. When a school bus is unloading children, it is equipped with a stop sign arm and flashing lights to alert drivers that they must stop. Drivers are only allowed to proceed after the stop sign arm is retracted, indicating that it is safe to do so. This protocol is crucial for protecting the safety of children who may be crossing the street or boarding the bus. The other answer choices highlight common misconceptions. Being in a hurry does not justify disregarding the law concerning school buses. The visibility of children is not a reliable measure, as children can appear suddenly and may not be visible at all times. Similarly, merely waiting for the lights to stop flashing does not offer adequate assurance of safety if the stop sign arm is still extended, as this indicates that children may still be in the vicinity. Therefore, adhering to the rule that allows movement only after the stop sign arm is completely retracted is essential for ensuring children's safety during bus stops.