Assertion `:-` Change in internal energy is zero for all gases at constant temperature.
Reason `:-` Internal energy is function of temperature only.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertiion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False

Answer

To solve the question regarding the assertion and reason about internal energy in gases, we will analyze both statements step by step.

### Step 1: Understanding the Assertion
The assertion states that "Change in internal energy is zero for all gases at constant temperature."

- For **ideal gases**, the internal energy (U) is a function of temperature only. Therefore, if the temperature remains constant (isothermal process), the change in internal energy (ΔU) is indeed zero.
- For **real gases**, however, the situation is more complex. While the internal energy is still primarily a function of temperature, it can also be influenced by intermolecular forces and pressure. Thus, for real gases, ΔU can change even if the temperature is constant.

**Conclusion for Assertion**: The assertion is **not true for all gases** because it does not hold for real gases.

### Step 2: Understanding the Reason
The reason states that "Internal energy is a function of temperature only."

- This statement is true for **ideal gases**, as their internal energy is solely dependent on temperature.
- However, for **real gases**, internal energy can depend on both temperature and pressure due to intermolecular forces. Therefore, this statement is not universally applicable.

**Conclusion for Reason**: The reason is **not true for all gases**, particularly for real gases.

### Final Conclusion
Both the assertion and the reason are false when considering all gases. Hence, the correct option is D: Both Assertion and Reason are false.