Answer:
A. burn the coal
Step-by-step explanation:
Burning the coal is only the way to convert the stored chemical energy of the coal into the the kinetic energy of its molecules that can then be transferred to the nearby objects in the form of heat by the various modes of heat transfer such as conduction, convection or radiation.
Conduction is the contact method of heat transfer in which the adjacent atom transfers the vibration kinetic energy.
Convection is the bulk mode of heat transfer in which the bulk mass of molecules moves near and far to the heat source.
Radiation is the distant mode of heat transfer in the form of electromagnetic waves.