Final answer:
OPTION B.
Convection is the primary method used in most central heating systems to deliver heat, involving the movement of warm air or water throughout a structure.
Step-by-step explanation:
Most central heating systems use convection as the method to deliver heat. Convection involves the movement of heat through fluids (gases or liquids) from a warmer area to a cooler one. In a typical central heating system, warm air or water is heated by a furnace or a boiler and then circulated throughout the house or building through ducts or pipes.
Conduction is the transfer of heat through direct contact and is less efficient in heating large spaces quickly. Radiation is the transmission of energy through electromagnetic waves and is not the primary method for central heating systems. However, it can complement convection, as in the case of radiators that emit heat both through convection as air circulates around them and through radiation directly warming nearby objects.