In which situation should you never fuel your bus?

Answer: B — In a closed building

Fueling a bus in a closed building is not permitted due to the significant fire and explosion hazards presented by fuel vapors. These vapors can accumulate in enclosed spaces, posing a serious risk to safety. Adequate ventilation is crucial during fueling to disperse any vapors, and a closed building typically lacks the necessary airflow. On the other hand, fueling at a designated rest area is designed for this purpose, providing an appropriate environment for refueling. Fueling while stopped at a red light or on a highway is not advisable due to safety concerns relating to traffic and the potential for accidents. However, the primary focus here is on the inherent dangers of fueling in an enclosed environment, which makes that option the most hazardous of all.