Right Answer is: A
Absolute Humidity is the actual amount of the water vapour present in the air. It tells the weight of water vapour per unit volume of air in terms of grams per cubic metre.
Relative Humidity is the percentage of moisture present in the atmosphere as compared to its full capacity (at a given temperature)
Specific Humidity is the weight of water vapour per unit weight of air. It is not affected by changes in pressure or temperature.