Question

what happens during heat transfer?
heat always flows from cool to warm.
heat always flows from warm to cool.
heat always flows from warm to hot.

Explanation:

Heat transfer occurs due to a temperature difference. According to the second law of thermodynamics, heat naturally moves from a region of higher temperature (warmer) to a region of lower temperature (cooler) until thermal equilibrium is reached.

Answer:

Heat always flows from warm to cool.