Why should divers avoid using EANx with high concentrations of oxygen for extended periods?

Using Enriched Air Nitrox (EANx) with high concentrations of oxygen for extended periods can result in oxygen toxicity, which is the correct reasoning for your answer. Oxygen toxicity can manifest both neurologically and pulmonarily when divers are exposed to elevated partial pressures of oxygen, particularly during deeper dives or when using mixtures with high oxygen content, such as EANx.

When the oxygen level exceeds safe limits, it can cause serious health issues, including seizures, chest pain, and difficulty breathing. The risks increase with both the depth of the dive and the duration of exposure to high oxygen levels. Understanding this aspect is crucial for divers who want to maintain safety and minimize risks associated with using EANx.

The other options, while they might relate to diving or its impacts, do not directly address the primary reason for avoiding prolonged exposure to high concentrations of oxygen in nitrox blends.