What should always be within reach on a school bus?

The correct answer highlights the importance of safety equipment on a school bus, specifically the fire extinguisher. A fire extinguisher must always be accessible to the driver or personnel in case of an emergency involving fire. It is crucial to have this equipment readily available since fires can develop quickly and pose a serious threat to the safety of the passengers, particularly children.

While other items like emergency exit windows ensure safe egress in emergencies, they are not equipment that is "within reach" during regular operations. Similarly, a first aid kit is essential for addressing medical emergencies, and safety cones are used for traffic control or marking hazards, but they do not specifically address immediate threats like a fire. Therefore, the fire extinguisher is prioritized as a critical safety measure that needs to be immediately accessible in the event of a fire emergency on the bus.