Which of the following is a type of fuel gas?

Propane is classified as a type of fuel gas because it is a hydrocarbon that is commonly used for heating, cooking, and in various industrial applications. It is a flammable gas at room temperature and pressure, and it exists in a gaseous state when not under pressure, but can be stored as a liquid in pressurized containers. Propane releases energy when burned, making it an effective fuel source.

In contrast, nitrogen is an inert gas that does not support combustion and is not used as a fuel. Hydrogen, while it is a flammable gas and can be used as a fuel, is typically considered separately from traditional fuel gases like propane. Argon, another inert gas, also does not burn or support combustion and is mainly used in welding and as an inert filler in various applications. Therefore, propane stands out as the correct answer due to its role as a combustible fuel gas used widely across different settings.