Which of the following describes a characteristic of Nitrox?

The correct answer highlights that Nitrox is a mixture of oxygen and nitrogen. Specifically, Nitrox refers to any gas mixture with a higher concentration of oxygen than the approximately 21% found in regular air, and a corresponding decrease in nitrogen. The primary purpose of using Nitrox, commonly known as Enriched Air Nitrox, is to reduce the amount of nitrogen a diver breathes in during a dive. This is beneficial as it lowers the risk of nitrogen narcosis and decompression sickness, allowing for longer bottom times and shorter surface intervals.

In contrast to this, the other options misrepresent the composition or characteristics of Nitrox. One choice suggests an increase in nitrogen content, which is contrary to the essence of what makes Nitrox advantageous for divers. Another choice incorrectly states that Nitrox is solely composed of oxygen, which disregards the fact that it includes nitrogen as well. Finally, while some advanced dive mixes may include helium, traditional Nitrox mixtures do not typically contain helium, making this option misleading in the context of standard Nitrox usage.