Which statement is true regarding heat transfer?

The statement that heat transfer can occur spontaneously from warmer to cooler objects accurately reflects the fundamental principles of thermodynamics. According to the second law of thermodynamics, heat naturally flows from areas of higher temperature to areas of lower temperature, resulting in an increase in entropy, or disorder, in a closed system. This spontaneous transfer is a natural process and does not require any external work.

The other statements do not align with established scientific principles. For example, the notion that heat only moves from cooler to warmer objects contradicts the second law of thermodynamics. Additionally, while energy conservation is a crucial concept in physics, it is important to clarify that while energy is conserved, the transformation of energy occurs, and the overall total does not decrease. Thus, the accurate understanding of heat transfer centers on the natural flow from warmer to cooler bodies.