Which MIL-STD pertains to O2 systems?

The correct choice concerning O2 systems is indeed related to MIL-STD 1330D. This standard outlines the requirements for oxygen systems used in aircraft and other military applications. Specifically, MIL-STD 1330D provides guidelines for the design, testing, and operational use of oxygen systems to ensure they meet safety and performance standards.

These systems are critical in aviation and underwater rescue operations, as they ensure that personnel receive the necessary oxygen supply during high-altitude flights or in environments where oxygen levels may be compromised. By adhering to the specifications in MIL-STD 1330D, manufacturers can ensure that the oxygen systems are reliable, efficient, and safe for use in operational conditions.

The other standards listed are related to different systems and applications, which is why they do not pertain to oxygen systems. Thus, understanding the standards and their specific applications helps ensure compliance and safety in military and rescue operations involving oxygen utilization.