An adiabatic process is one in which :-

Options

A. Temperature of the system does not change
B. The system is not closed to heat transfer
C. There is no entropy change
D. None of these

Answer

To solve the question regarding the characteristics of an adiabatic process, we will analyze the options provided and determine which statement accurately describes an adiabatic process.

### Step-by-Step Solution:

1. **Understanding Adiabatic Process**:
An adiabatic process is defined as a thermodynamic process in which there is no heat transfer (Q = 0) between the system and its surroundings.

**Hint**: Remember that "adiabatic" means "no heat exchange".

2. **Evaluating the First Option**:
The first option states that "the temperature of the system does not change". In an adiabatic process, although no heat is exchanged, the temperature can change due to work done on or by the system. Therefore, this statement is incorrect.

**Hint**: Consider how work can affect temperature even when heat is not transferred.

3. **Evaluating the Second Option**:
The second option claims that "the system is not closed to heat transfer". This is contradictory to the definition of an adiabatic process, where heat transfer is indeed absent. Thus, this statement is also incorrect.

**Hint**: Recall the definition of a closed system versus an adiabatic process.

4. **Evaluating the Third Option**:
The third option states that "there is no entropy change". The change in entropy (ΔS) is given by the formula ΔS = Q/T. Since Q = 0 in an adiabatic process, it follows that ΔS = 0, indicating that there is no change in entropy. This statement is correct.

**Hint**: Think about how entropy relates to heat transfer and its implications in an adiabatic process.

5. **Evaluating the Fourth Option**:
The last option states "none of these". Since we have identified that the third option is correct, this statement is incorrect.

**Hint**: If one of the options is correct, this option cannot be true.

### Conclusion:
Based on the analysis, the correct answer is that in an adiabatic process, "there is no entropy change" (Option C).