Assertion : In an adiabatic process, change in internal energy of a gas is equal to work done on/by the gas in the process.
Reason : This is because temp.of gas remains constant in an adiabatic process.

Options

A. If both assetion and reason are true and reaasons is the correct expanation of assetion
B. If both assetion and reason are tur but reason is not the correct explanation of assetion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Explanation

To solve the question, we need to analyze the assertion and the reason given in the context of thermodynamics, particularly focusing on adiabatic processes.

### Step-by-step Solution:

1. **Understanding the Assertion**:
- The assertion states that in an adiabatic process, the change in internal energy (ΔU) of a gas is equal to the work done (W) on or by the gas.
- According to the first law of thermodynamics, we have:
\[ dQ = dU + W \]
- For an adiabatic process, there is no heat exchange with the surroundings, which means:
\[ dQ = 0 \]
- Therefore, we can rewrite the first law as:
\[ 0 = dU + W \implies dU = -W \]
- This indicates that the change in internal energy is equal to the negative of the work done by the gas. If work is done on the gas, ΔU is positive, and if work is done by the gas, ΔU is negative.

2. **Understanding the Reason**:
- The reason states that the change in internal energy is equal to the work done because the temperature of the gas remains constant in an adiabatic process.
- However, this statement is incorrect. In an adiabatic process, the temperature of the gas does not remain constant; it changes. The internal energy of an ideal gas is related to its temperature, given by:
\[ \Delta U = nC_v \Delta T \]
- Since ΔU is not zero in an adiabatic process, ΔT cannot be zero either. Therefore, the temperature of the gas changes during an adiabatic process.

3. **Conclusion**:
- The assertion is correct: the change in internal energy of a gas in an adiabatic process is indeed equal to the work done on or by the gas.
- The reason is incorrect: the temperature of the gas does not remain constant in an adiabatic process; it changes.

Thus, we conclude that the assertion is true, but the reason is false.

### Final Answer:
- Assertion: True
- Reason: False