Which hydraulic systems are used to pressurize the APU accumulators?

The correct choice, indicating that the left APU accumulator is pressurized by the #1 hydraulic system while the right APU accumulator is pressurized by the #4 hydraulic system, reflects the specific design and functionality of the C-5's hydraulic systems. In the C-5, the APU accumulators rely on separate hydraulic systems for their pressurization to ensure redundancy and reliability in operation.

This design is significant because it means that even if one hydraulic system fails, the other can still maintain functionality, enhancing the safety and performance of the APU. The different systems being utilized for each accumulator also allows for better load distribution and can help in balancing hydraulic pressures throughout the aircraft.

Other options discussing the use of the #3 or #2 hydraulic systems do not align with the established design principles and operational requirements of the C-5’s hydraulic setup, which specifically designates these particular systems for the APU accumulators. Thus, understanding the rationale behind the choice clarifies the importance of hydraulic system configurations in ensuring operational efficacy and reliability.