When the temperature of the air becomes almost equal to the dew point the air becomes saturated and the relative humidity during this condition becomes 100%. If the temperature of the air decrease below the dew point the relative humidity will be 100% or exceeds 100%. This condition, when the temperature of the air decreases below the dew point is called supersaturation but most of the time the temperature of the air will be lower than the dew point.
Answer: B. Osmosis Across a Membrane
The movement of water across a gradient is called osmosis.
