ANS:D - all (a), (b) and (c).

The rate of heat transfer by vaporization from pools of water is indeed affected by several factors: (a) The nature of the heating surface and distribution of bubbles: The efficiency of heat transfer can vary depending on the surface characteristics of the heating element and how effectively bubbles are distributed throughout the water. (b) Surface tension of water: Surface tension affects the formation and stability of bubbles. Higher surface tension may inhibit bubble formation, which could affect the rate of heat transfer. (c) Viscosity of water: Viscosity affects the ability of water to flow and the movement of bubbles within the liquid. Higher viscosity may hinder bubble movement and heat transfer. So, the correct answer is (d) all of the above (a), (b), and (c).