Which of the following is an appropriate method to purge moisture from an oxygen system?

The use of dry nitrogen to purge moisture from an oxygen system is appropriate because nitrogen is an inert gas that does not support combustion and can effectively displace moisture. When purging an oxygen system, it's crucial to remove moisture to prevent oxidation and the potential formation of corrosive compounds, which could compromise the integrity and safety of the system.

Dry nitrogen, being free of water vapor, helps create a dry environment that ensures the system is not adversely affected by the presence of moisture. This method is widely accepted in the aerospace industry as a safe and effective way to maintain the reliability and performance of oxygen systems.

Compressed air is not suitable for this purpose, as it contains moisture which could introduce additional water vapor into the system. Liquid oxygen poses significant safety risks, including the potential for combustion and extreme hazards, while water vapor clearly is not a purging agent and would increase the moisture content instead of reducing it.