Assertion : Desilverisation of lead is done by Parke's method.
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 will break down the concepts involved in the Parkes method of desilverization of lead and the role of zinc in this process.

### Step 1: Understanding the Assertion
The assertion states that "Desilverisation of lead is done by Parke's method."

- **Explanation**: The Parkes method is a well-known metallurgical process used to separate silver from lead. This method is particularly effective when dealing with lead-silver alloys.

### Step 2: Understanding the Reason
The reason given is "When lead-silver alloy is poor in silver, zinc is added to molten ore."

- **Explanation**: In the Parkes method, when the lead-silver alloy has a low concentration of silver, zinc is added to the molten lead. Zinc has a higher affinity for silver compared to lead. When zinc is introduced, it forms a zinc-silver alloy, which can be easily separated from the lead.

### Step 3: Analyzing the Relationship Between Assertion and Reason
Now we need to evaluate if the reason supports the assertion.

- **Explanation**: The assertion is true as the Parkes method is indeed used for desilverizing lead. The reason is also true because adding zinc to the molten lead-silver alloy helps in extracting silver when the alloy is low in silver content. Therefore, both the assertion and reason are correct, and the reason provides a valid explanation for the assertion.

### Conclusion
Both the assertion and reason are true, and the reason correctly explains the assertion.

### Final Answer
The correct answer is: **Both Assertion and Reason are true, and the Reason is the correct explanation for the Assertion.**

---