Answer:
Option B:
Conduction
Step-by-step explanation:
Conduction is the transfer of heat from one molecule to another between two solids that are in direct contact with each other. For the conduction of heat to occur, the medium involved must be solid. This is because the molecules of solids are closely packed together and they cannot freely move about. The heat flowing through them can easily be passed on from one molecule to the other until it reaches all the parts of the object. This is exactly what will happen to the iron bar. Thermal energy from one end of the bar will get transferred between the molecules of the iron bar until it reaches the other end.
Convection on the other hand involves the transfer of heat through a liquid medium.
Radiation involves teh transfer of heat in a vacuum.