Which scenario is allowed for a standby diver to be deployed?

The correct answer is anchored on the specific conditions under which a standby diver can be safely deployed. In underwater operations, conditions are critical for ensuring the safety of divers, and option C outlines specific parameters that contribute to this safety.

Deploying a standby diver under conditions of no decompression (no deco diving) means that the diver can safely ascend to the surface without the need for staged decompression stops. This significantly reduces the risks associated with decompression sickness. Additionally, stipulating the same job and location focuses the standby diver’s role on immediate assistance to their colleague without the added hazards of changing environments or tasks. Furthermore, being surface-supplied eliminates potential issues that can occur with scuba tanks, such as running out of air. This combination of factors results in a scenario that maximizes diver safety and readiness for emergencies.

The other scenarios mentioned do not maintain the same level of safety assurance, either because they involve variables that could introduce risk or because they lack certain critical safety protocols, thus making them less suitable for deploying a standby diver.