Why does placing an unresponsive victim on their back over a rescue tube create an advantageous position?

Placing an unresponsive victim on their back over a rescue tube is beneficial because the flotation provided by the tube keeps the individual at the water's surface. This positioning is critical in aquatic rescues, as it ensures that the victim remains as buoyant as possible, minimizing the risk of submersion and allowing for easier access by the rescuer. Along with flotation, this position supports easier retrieval and transportation of the victim, which can be essential in emergency situations where time is of the essence.

While the other options mention important aspects of rescue techniques, they do not directly address the crucial benefit of flotation in this context. The ability to monitor vital signs requires a stable position for the rescuer and the victim, but the primary function of the tube here is to ensure that the victim stays above water. Similarly, while self-rescue may be a desirable outcome, an unresponsive victim would not have the capability to assist themselves; thus, maintaining their position with flotation is vital.