What is the definition of residual nitrogen in diving?

Residual nitrogen refers to the nitrogen that remains dissolved in a diver's bloodstream and tissues after the ascent from a dive. When divers descend, they inhale air that contains nitrogen, which is absorbed by the body due to the increased pressure. Upon surfacing, some of this nitrogen can remain in the body, especially if the diver has been exposed to increased depths or longer durations. This residual nitrogen is important to consider because it affects future dives and must be managed to avoid decompression sickness, commonly known as "the bends."

The options highlight different aspects of nitrogen management in diving, but only the correct answer specifically addresses the presence of excess nitrogen in the body post-dive, which is crucial for understanding dive safety and planning for subsequent dives.