A process is said to be reversible if

Options

A. the system return to their original states
B. the surrounding return to their original states
C. both the system as well as the surrounding return to their original states
D. neither system nor surroundings return to their original states

Answer

To determine the conditions under which a process is said to be reversible, we will analyze the definitions and characteristics of reversible processes in thermodynamics.

### Step-by-Step Solution:

1. **Understanding Reversible Processes**:
A reversible process is defined as a thermodynamic process that can be reversed without leaving any change in both the system and the surroundings.

2. **Equilibrium Condition**:
During a reversible process, the system is always in a state of equilibrium with its surroundings. This means that at every stage of the process, the system and the surroundings can be restored to their initial states without any net change.

3. **Returning to Original States**:
For a process to be reversible, both the system and the surroundings must be able to return to their original states after the process has occurred. This implies that the changes that occurred during the process can be undone.

4. **Evaluating Options**:
- **Option A**: The system returns to its original state. (Partially correct, but not sufficient)
- **Option B**: The surroundings return to their original states. (Partially correct, but not sufficient)
- **Option C**: Both the system and the surroundings return to their original states. (Correct)
- **Option D**: Neither the system nor the surroundings return to their original states. (Incorrect)

5. **Conclusion**:
The correct definition of a reversible process is that both the system and the surroundings must return to their original states. Therefore, the answer is **Option C**.

### Final Answer:
A process is said to be reversible if both the system as well as the surroundings return to their original states.

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