Assertion: In Mond process, nickel is heated in a stream of CO forming a volatile complex.
Reason: This is an electrolytic refining method.

Options

A. Assertion and reason both are correct statements but reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that in the Mond process, nickel is heated in a stream of carbon monoxide (CO) to form a volatile complex. This is indeed true. In the Mond process, nickel reacts with carbon monoxide to form nickel tetracarbonyl (Ni(CO)₄), which is a volatile compound.

2. **Chemical Reaction**: The chemical reaction that occurs in the Mond process can be represented as:
\[ \text{Ni (s) + 4 CO (g) } \rightarrow \text{ Ni(CO)₄ (g)} \]
This reaction indicates that solid nickel reacts with gaseous carbon monoxide to form a gaseous complex.

3. **Temperature Consideration**: The formation of nickel tetracarbonyl occurs at around 250 K, which is a low temperature, allowing the complex to remain in the gaseous state.

4. **Separation of the Volatile Compound**: The volatile nickel tetracarbonyl is then separated from the other materials.

5. **Decomposition of Nickel Tetracarbonyl**: Upon heating the nickel tetracarbonyl at a higher temperature (around 450 K), it decomposes back into pure nickel and carbon monoxide:
\[ \text{Ni(CO)₄ (g) } \rightarrow \text{ Ni (s) + 4 CO (g)} \]
This confirms that the assertion is correct.

6. **Understanding the Reason**: The reason states that the Mond process is an electrolytic refining method. This is incorrect. The Mond process is classified as a vapor phase refining method, not electrolytic refining.

7. **Conclusion**: Therefore, the assertion is true while the reason is false. The correct classification of the Mond process is vapor phase refining, not electrolytic refining.

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