ANS:C - both 'a' & 'b'

The effect of friction on the flow of steam through a nozzle is to decrease the mass flow rate of steam. Friction between the steam and the walls of the nozzle causes energy losses in the form of heat and work, which reduces the kinetic energy and velocity of the steam flowing through the nozzle. As a result, the mass flow rate of steam decreases. Friction does not directly affect the wetness of steam. Wetness of steam refers to the moisture content in the steam, which is primarily influenced by factors such as the steam generation process and temperature. While friction may indirectly affect wetness through changes in temperature or pressure, its primary effect is on the mass flow rate of steam. So, the correct answer is: neither 'a' nor 'b'.