How should safety controls or protective devices be connected?

The correct answer indicates that safety controls or protective devices should be connected to interrupt the underground conductor and shut off fuel flow. This method is essential in ensuring that in the event of a malfunction or unsafe condition, the flow of fuel can be immediately stopped to prevent potential hazards such as leaks, fires, or explosions.

Connecting safety devices in this manner provides a fail-safe mechanism, allowing for an automatic or manual intervention to safely halt operations. This setup not only meets safety regulations but also safeguards both property and human life by mitigating risks associated with fuel handling.

The other options suggest methods that do not prioritize direct and effective interruption of fuel flow in a hazardous situation. For instance, connecting directly to the fuel line or in series with the heater might not offer the immediate safety response needed in emergencies. Meanwhile, relying solely on a remote switch may restrict accessibility and instant action in critical moments.