Final answer:
The relative humidity of expired gas during exhalation varies little between different individuals, being consistently high and close to saturation due to the humidifying effect of the lungs and respiratory tract.
Step-by-step explanation:
During exhalation, the relative humidity of expired gas varies little between different individuals. When air is exhaled from the lungs, it typically has a high water vapor content, which produces a humidity close to saturation, regardless of the external temperature, whether it's a cold or warm environment. This relative consistency in expired gas humidity among individuals holds true regardless of the temperature and humidity conditions outside of the body, as the lungs and respiratory tract ensure the air is warmed and humidified to this level during inhalation and before exhalation.