What safety feature is included in the MK-20 system to manage underwater pressure changes?

The inclusion of pressure relief valves in the MK-20 system serves a critical purpose in managing underwater pressure changes. These valves are designed to automatically release excess pressure that might build up within the diving system as a diver descends to greater depths. This feature is essential because underwater pressure increases significantly with depth, and if the internal pressure within the system were to exceed safe levels, it could result in equipment failure or potential harm to the diver.

By allowing for the safe release of excess pressure, pressure relief valves help maintain the integrity of the dive equipment and ensure the safety of the diver, enabling a more controlled experience while submerged. This feature reflects the importance of managing environmental factors in diving operations, as failure to do so could jeopardize not just the equipment but also the diver's safety.

The other options, while relevant to diving operations, do not specifically address the direct management of underwater pressure changes in the same way that pressure relief valves do.