ANS:C - Both (a) and (b)

During a sensible cooling process, both the specific humidity and the partial pressure of vapor remain constant. Explanation:

1. Sensible Cooling Process:
   • Sensible cooling refers to a process where the temperature of a substance decreases without a phase change occurring.
   • During sensible cooling, the substance releases heat to its surroundings, resulting in a decrease in temperature while the phase remains unchanged.
2. Specific Humidity:
   • Specific humidity is the ratio of the mass of water vapor to the total mass of air (including dry air and water vapor) in a given volume.
   • During sensible cooling, the total mass of water vapor in the air remains constant because no phase change occurs. Therefore, the specific humidity remains constant.
3. Partial Pressure of Vapor:
   • The partial pressure of vapor is the pressure exerted by the water vapor molecules in a mixture of gases.
   • In a closed system undergoing sensible cooling, the total pressure remains constant, and since the specific humidity remains constant, the partial pressure of vapor also remains constant.
4. Conclusion:
   • Both the specific humidity and the partial pressure of vapor remain constant during a sensible cooling process because there is no change in the amount of water vapor present in the air; only its temperature decreases.