Based on the principles of convection, conduction and thermal radiation, which scenario below is most similar to the following situation?

you put a heating pad on your back after exercising.
a) feeling a metal wire get warmer as you roast a marshmallow over a fire.
b) warm air rising in a room where the air is moving.
c) the sun warming up the roof on a house.
d) cold water sinking in a pot of water being warmed up on the stove.