What components does the Hot Battery bus provide power to with the battery switch off?

The Hot Battery bus is designed to supply power to essential systems even when the battery switch is turned off. This ensures that critical components can still function in case of an emergency or when the aircraft is not powered up entirely. The correct choice highlights components such as Firewall Shutoff Valves, Engine Fire Extinguishing Control Switches, Entry Lights, and Ground Heat, all of which are vital for safety and operational readiness.

These components are necessary to ensure that the aircraft can be managed effectively, even in situations where the main power is not available. For instance, the Firewall Shutoff Valves are crucial for controlling fuel flow in the event of an engine fire; they require a power source to operate correctly. Similarly, the Engine Fire Extinguishing Control Switches must be operable to activate fire suppression measures promptly. Entry lights and ground heat are other essential functions that help ensure safe operations while on the ground.

In contrast, the other options listed either pertain to components that do not require continuous power when the battery switch is off or are not as critical for immediate emergency responses as those provided by the Hot Battery bus. Thus, the correct answer reflects essential systems that maintain safety and basic functionality even when the aircraft's main systems are inactive.