Which of the following assist heat in the spread of fire?

The correct answer highlights the three primary mechanisms that assist in the transfer of heat during a fire: conduction, convection, and radiation.

Conduction involves the direct transfer of heat through solid materials. When one material is heated, it can transfer that heat to another material that is in contact with it, allowing fire to spread through solid objects.

Convection refers to the movement of heat through fluids—this includes both liquids and gases. Warm air rises and can carry heat away from the fire, allowing flames to propagate to areas further away from the original source and potentially igniting nearby combustibles.

Radiation is the transfer of heat in the form of electromagnetic waves. This allows heat energy to radiate away from the fire without needing a medium, meaning it can ignite materials at some distance from the flames.

Together, these three mechanisms encompass the ways in which heat can move and contribute to the spread of fire, making them crucial elements in fire behavior.

The other options mention terms that do not directly pertain to mechanics of heat transfer related to fire spread, such as evaporation and reactivity, which play different roles in fire dynamics.