In Treatment Table 4, what is the recommended breathing schedule once at a 60-foot stop?

The correct choice outlines an essential protocol in decompression procedures while utilizing oxygen at a 60-foot stop. Treatment Table 4, part of the Navy Dive Manual, indicates a specific breathing schedule that optimizes the off-gassing of inert gases absorbed during the dive, particularly nitrogen. When divers reach a stop depth of 60 feet, the recommended duration of 25 minutes on oxygen followed by 5 minutes on air ensures that divers receive a significant amount of oxygen to help remove absorbed nitrogen from their bodies efficiently, thus reducing the risk of decompression sickness.

During the periods spent on oxygen, it provides a physiological benefit by delivering higher partial pressures of oxygen, which aids in the elimination of nitrogen more effectively than air would alone. The brief interval on air helps maintain a safe environment while limiting oxygen toxicity, aligning with protocols meant for safe decompression and recovery. This carefully structured schedule emphasizes the importance of time management for gas exchanges necessary in underwater scenarios.