Which system does the C-5 APU primarily support for temperature regulation and comfort?

The Auxiliary Power Unit (APU) on the C-5 primarily supports the air conditioning system. The APU generates electrical power and provides bleed air, which is crucial for operating the air conditioning system while the aircraft is on the ground or when the main engines are not running. This capability is essential for regulating the temperature and maintaining comfort for crew and passengers during ground operations or in-flight situations where engine-driven systems might not be available.

While the catering system benefits from the APU's power and air supply indirectly, as it may use electrical systems and conditioned air for food storage and preparation, the direct purpose of the APU is closely aligned with air conditioning. The fuel management and landing gear systems do not rely on the APU for temperature regulation, making them less relevant in this context. Thus, choosing the air conditioning system accurately reflects the primary function of the APU in regards to temperature control and comfort on the C-5 aircraft.