Answer:

Explanation:

In thermodynamics, enthalpy, entropy, and energy are all important properties that describe the state of a system and the energy changes that occur during a process. These properties can be positive or negative depending on the specific conditions and processes involved.

Change in enthalpy:
Enthalpy is a measure of the total heat content of a system. It represents the sum of the internal energy of the system and the product of pressure and volume. The change in enthalpy (ΔH) can be positive or negative, depending on whether heat is absorbed or released by the system during a process. If heat is absorbed, the change in enthalpy is positive, and if heat is released, the change in enthalpy is negative. Therefore, the change in enthalpy can be either positive or negative.

Change in entropy:
Entropy is a measure of the degree of disorder or randomness in a system. The change in entropy (ΔS) can also be positive or negative, depending on the direction of the process. If the process leads to an increase in disorder, the change in entropy is positive. If the process leads to a decrease in disorder, the change in entropy is negative. Therefore, the change in entropy can be either positive or negative.

Change in energy:
Energy is a fundamental property that can exist in different forms, such as kinetic energy, potential energy, or thermal energy. The change in energy (ΔE) can also be positive or negative, depending on whether energy is gained or lost by the system during a process. If energy is gained, the change in energy is positive, and if energy is lost, the change in energy is negative. Therefore, the change in energy can be either positive or negative.

Conclusion:
Based on the explanations above, the correct answer is option 'D' - None of these. None of the given options - change in enthalpy, change in entropy, or change in energy - are restricted to be always positive or negative. These properties can vary depending on the specific conditions and processes involved in a thermodynamic system.