ANS:A - humidified with wet bulb temperature decreasing.

When unsaturated air is passed through a water spray chamber maintained at a temperature below its initial wet bulb temperature, the air will be cooled and humidified, and the wet bulb temperature will decrease. Here's why:

1. Cooling: The water spray chamber is maintained at a temperature lower than the initial wet bulb temperature of the air. As the unsaturated air comes into contact with the water droplets in the chamber, heat is transferred from the air to the water droplets through evaporation. This leads to a decrease in the temperature of the air.
2. Humidification: As the air cools, its ability to hold moisture decreases. This causes some of the water vapor in the air to condense into liquid water droplets, effectively increasing the humidity of the air. Therefore, the air becomes more humid as it passes through the water spray chamber.
3. Decrease in Wet Bulb Temperature: The wet bulb temperature represents the lowest temperature achievable by evaporative cooling. As the air is cooled and humidified in the water spray chamber, its wet bulb temperature decreases because the process of evaporation from the water droplets lowers the temperature of the air.