Which of the following is NOT a common gas found in water?

Sodium chloride, commonly known as table salt, is not a gas but an ionic compound that dissolves in water to produce sodium and chloride ions. In contrast, hydrogen sulfide, carbon dioxide, and methane are all gases that can exist in natural water bodies. Hydrogen sulfide can be produced by the decomposition of organic matter in anaerobic conditions, carbon dioxide is naturally dissolved in water as a result of atmospheric exchange and respiration processes, and methane can be present in groundwater due to organic matter decomposition. Understanding the states of matter and the common substances in water is crucial for water quality management and analysis, especially in the context of drinking water standards and environmental assessments.