ANS:D - all (a), (b) & (c)

The loss of heat from an untagged steam pipe to the ambient air can occur through all of the following mechanisms:

• Conduction: Heat transfer through the material of the pipe itself.
• Convection: Heat transfer due to the movement of fluid (air) over the surface of the pipe, carrying away heat.
• Radiation: Heat transfer through electromagnetic waves emitted by the surface of the pipe.