ANS:A - gas

The dew point of a saturated gas phase equals the gas temperature. The dew point is the temperature at which air becomes saturated with water vapor and starts to condense into liquid water. When the temperature of a gas decreases to its dew point, the gas is said to be at 100% relative humidity. At this point, further cooling will result in condensation of water vapor into liquid water. The dew point is directly related to the temperature of the gas phase itself. It indicates the temperature at which the gas is saturated with water vapor, and condensation begins to occur. Therefore, the dew point temperature corresponds to the temperature of the gas phase, not the room temperature, wet bulb temperature, or any other external temperature.