ANS:A - decreases & increases.

When wet steam is throttled but still remains wet at the exit of the throttle valve, its temperature decreases and dryness fraction increases. Throttling is a process in which the pressure of a fluid is reduced by allowing it to flow through a constriction, such as a valve or nozzle, without any work being done on or by the fluid. When wet steam is throttled, it undergoes a reduction in pressure without any significant change in enthalpy. As wet steam passes through the throttle valve and its pressure decreases:

1. Temperature: According to the steam tables, when pressure decreases, the temperature of the steam also decreases due to the reduction in internal energy. Therefore, the temperature of the wet steam decreases during throttling.
2. Dryness Fraction: Since no phase change (such as condensation or vaporization) occurs during throttling, the mass fraction of water vapor in the wet steam remains the same, while the mass fraction of dry steam (vapor) increases relative to the total mass. Consequently, the dryness fraction of the steam increases.