Difficulty: Medium
Correct Answer: The ratio of the actual mass of water vapor in a given volume of moist air to the mass of water vapor in the same volume of saturated air at the same temperature and pressure.
Explanation:
Concept
“Percentage humidity” (often used interchangeably with degree of saturation in basic MCQ contexts) compares actual vapor content to saturated vapor content at the same T and p, on a per volume basis.
Option analysis
(A) Absolute humidity (vapor density in a given volume of dry air).(B) Humidity ratio/specific humidity (mass basis per kg dry air).(C) Often used to describe relative humidity in mass-per-mass terms, but the classical “percentage humidity” definition aligns with (D).
Final Answer
The ratio based on equal volumes at the same T and p — option (D).
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