To understand the implications of the second law of thermodynamics. The second law of thermodynamics explains the direction in which the thermodynamic processes tend to go. That is, it limits the types of final states of the system that naturally evolve from a given initial state. The second law has many practical applications. For example it explains the limits of efficiency for heat engines and refrigerators. To develop a better understanding of this law, try these conceptual questions.

The thermodynamic processes that occur in nature ____________.
(A) convert thermal energy into mechanical energy
(B) lead to a more ordered state
(C) cannot be reversed
(D) do not conserve energy

The thermodynamic process is a process in which the thermal or heat energy is converted into mechanical energy and some amount of energy goes into surroundings. That means, the total amount of energy is not converted into mechanical energy.

Or we can say that the energy can not be created or destroyed, it can only change or transfer from one state to another state.

The thermodynamic process is not a reversible process that means it is an irreversible process.

Hence, the correct option is, (C) cannot be reversed