Concept:Temperature decides the direction of heat flow between two bodies in contact.
Explanation:Heat always flows from a body at higher temperature to a body at lower temperature.
When two bodies touch, the transfer of heat continues until both attain the same temperature, called thermal equilibrium.
Temperature measures the degree of hotness or coldness of a body, reflecting the average kinetic energy of its particles.
This natural direction of heat flow is described by the second law of thermodynamics.
Thus, temperature, not heat capacity, mass, or power, determines which way heat will move.
Answer:Option D. Temperature.