Assertion : Desilverisation of lead is done by Parke's method `DeltaG`.
Reason : When lead-silver alloy is poor in silver, zinc is added to molten ore.

Options

A. If both assetion and reason are CORRECT, and reason is the CORRECT explanation of the assertion
B. If both assertion and reason are CORRECT, but reason is NOT the CORRECT explanation of the assertion
C. If assertion is CORRECT but reason is INCORRECT
D. If assertion is INCORRECT but reason is CORRECT

Answer

To analyze the assertion and reason provided in the question, we need to break down the concepts involved in the desilverization of lead using Parkes' method.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Desilverisation of lead is done by Parke's method".
- Parkes' method is indeed a well-known process for removing silver from lead. It involves adding zinc to molten lead, which preferentially combines with silver to form a zinc-silver alloy.

2. **Understanding the Reason**:
- The reason states that "When lead-silver alloy is poor in silver, zinc is added to molten ore."
- This statement is somewhat misleading. Zinc is added to the molten lead-silver alloy, not to the ore itself. The purpose of adding zinc is to extract silver from the lead when the alloy contains a low concentration of silver.

3. **Analyzing the Process**:
- In Parkes' method, when zinc is added to molten lead, it forms a separate layer because zinc is not miscible with lead.
- The solubility of silver in zinc is significantly higher than in lead. Therefore, silver will preferentially migrate into the zinc layer, allowing for its separation from lead.

4. **Conclusion**:
- The assertion is correct as Parkes' method is indeed used for desilverization of lead.
- The reason is misleading because it incorrectly states that zinc is added to the ore instead of the molten lead-silver alloy.

5. **Final Answer**:
- The correct answer is that the assertion is true, but the reason is false.