Assertion : `Ag_(2) S` + 4 KCN `hArr` `2K [Ag(CN)_(2)] + K_(2) S`
Reason : The reaction is carried out in the presence of `O_(2)` so that `K_(2)S` is oxidised to `K_(2) SO_(4)` thereby shifting the equilibrium in forward direction.

Options

A. Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement-1
B. Statement-1 is True, Statement-2 is True, Statement-2 is NOT a correct explanation for Statement-1
C. Statement-1 is True, Statement-2 is False.
D. Statement-1 is False, Statement-2 is True.

Explanation

To solve the given question, we need to analyze the assertion and reason provided, and determine their validity and relationship.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states:
\[ \text{Ag}_2\text{S} + 4 \text{KCN} \rightleftharpoons 2 \text{K[Ag(CN)}_2] + \text{K}_2\text{S} \]
- This reaction indicates that silver sulfide (Ag₂S) reacts with potassium cyanide (KCN) to form potassium dicyanoargentate (K[Ag(CN)₂]) and potassium sulfide (K₂S).

2. **Validity of the Assertion**:
- The assertion is true because the reaction is indeed a valid chemical reaction that occurs under certain conditions.

3. **Understanding the Reason**:
- The reason states that the reaction occurs in the presence of oxygen, which oxidizes K₂S to K₂SO₄, thereby shifting the equilibrium in the forward direction.
- The reaction for the oxidation of K₂S can be represented as:
\[ \text{K}_2\text{S} + 2 \text{O}_2 \rightarrow \text{K}_2\text{SO}_4 \]

4. **Validity of the Reason**:
- The reason is also true. The presence of oxygen can lead to the oxidation of K₂S to K₂SO₄, which would decrease the concentration of K₂S in the reaction mixture.

5. **Application of Le Chatelier's Principle**:
- According to Le Chatelier's principle, if a system at equilibrium is disturbed by changing the concentration of a reactant or product, the system will shift in the direction that counteracts the disturbance.
- In this case, as K₂S is consumed to form K₂SO₄, the equilibrium will shift to the right to produce more K₂S and thus favor the formation of products (K[Ag(CN)₂]).

6. **Conclusion**:
- Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is that both statements are true, and the reason is a correct explanation of the assertion.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation for the assertion.