Which of the following best describes Classical Thermodynamics?

Classical Thermodynamics is fundamentally grounded in experimental data and theoretical postulates, allowing it to describe the macroscopic behavior of systems in terms of quantities like temperature, pressure, and volume. It provides a framework for understanding energy transfer, work, and heat in various processes, primarily by observing and measuring these macroscopic properties under different conditions. The reliance on empirical data is critical, as it helps establish the laws of thermodynamics, such as the first and second laws, which govern energy conservation and entropy.

The theoretical postulates help in providing a structured approach to problem-solving in thermodynamics, enabling predictions about how systems will behave under different sets of conditions. This approach is crucial for applications across numerous fields, including engineering and physical sciences.

In contrast, other aspects mentioned in the other options focus either on specific types of systems, such as equilibrium or irreversible processes, or delve into statistical mechanics, which is a separate but related discipline that connects microscopic particle behavior to macroscopic thermodynamic phenomena. Thus, emphasizing the empirical and theoretical foundation of classical thermodynamics makes option C the most accurate description.