The correct option regarding the direction of heat transfer is A: heat is always transferred from the hotter object to the cooler object.
This principle is aligned with the second law of thermodynamics, which states that heat naturally flows from a region of higher temperature to a region of lower temperature until thermal equilibrium is reached.
The other options you provided are not accurate representations of how heat transfer works. Here's a brief clarification on why:
- B: This is incorrect because heat does not flow from cooler to warmer objects.
- C: While the motion of particles is related to temperature, the statement does not accurately describe the heat transfer process.
- D: While it is true that objects with higher average kinetic energy are hotter, the statement does not clearly convey the direction of heat transfer, which is always from higher to lower temperature.
Therefore, the best choice is A.