Which statement is true about the MK 25 Mod 2?

• A. The three major components are pneumatic system, recirculation system, and the equipment case/harness subsystem
• B. The MK 25 Mod 2 has four major subsystems
• C. The exhalation hose has no unique fittings
• D. The breathing bag capacity is 6 liters

Answer: (A)

The MK 25 Mod 2 is organized around three major subsystems: the pneumatic system, which regulates gas supply and control; the recirculation system, which forms and manages the breathing loop; and the equipment case/harness subsystem, which houses and supports all components and provides attachment points for the diver. This structure explains why describing three major components is correct—the unit is built around these three functional blocks that together enable breathing, gas management, and physical integration.

Understanding the recirculation system helps you see how the loop keeps breathing gas viable: it routes gas through the loop, supports the scrubber and related flow paths, and maintains the closed-circuit operation that divers rely on for extended dives. The pneumatic system is what ensures the right pressures and flow rates are delivered to the diver, while the equipment case/harness subsystem provides the rugged housing and mounting for reliability in harsh underwater conditions.

The other statements don’t fit because there aren’t four major subsystems in the MK 25 Mod 2, and the design includes intentional, unique fittings on components like the exhalation hose to prevent misassembly. Also, the breathing bag isn’t six liters in capacity; its volume is much smaller, sized to fit the breathing loop without adding unnecessary bulk.