Which of the following phenomenon will exhibit the minimum heat transfer?

ANS:D - Conduction in air.

Conduction in air will exhibit the minimum heat transfer among the listed phenomena. Conduction is the transfer of heat through a material without any movement of the material itself. Air is a poor conductor of heat compared to liquids and solids. Therefore, heat transfer by conduction through air is relatively low. Boiling, forced convection in air, and free convection in air involve fluid motion, which can significantly enhance heat transfer compared to conduction alone. Among these, conduction in air will have the least amount of heat transfer.