Assertion : In the reaction `H_2 S + HNO_3 to NO + S + H_2 O, HNO_3` acts as an oxidising agent.
Reason : `HNO_3` gets oxidised to NO.

Options

A. If both Assertion 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 solve the question, we need to analyze the assertion and reason statements regarding the reaction between \(H_2S\) and \(HNO_3\).

### Step-by-Step Solution:

1. **Identify the Reaction**:
The reaction given is:
\[ H_2S + HNO_3 \rightarrow NO + S + H_2O \]

2. **Determine Oxidation States**:
- For \(H_2S\):
- Hydrogen (H) has an oxidation state of +1 (2 H = +2).
- Sulfur (S) has an oxidation state of -2.
- Overall oxidation state of \(H_2S\) = +2 + (-2) = 0.
- For \(HNO_3\):
- Hydrogen (H) = +1, Oxygen (O) = -2.
- Nitrogen (N) = +5 (to balance the overall charge).
- For \(NO\):
- Oxygen (O) = -2, thus Nitrogen (N) = +2.
- For elemental Sulfur (S):
- Oxidation state = 0.
- For \(H_2O\):
- Hydrogen (H) = +1, Oxygen (O) = -2.

3. **Calculate Changes in Oxidation States**:
- In \(H_2S\), sulfur changes from -2 to 0 (oxidation).
- In \(HNO_3\), nitrogen changes from +5 to +2 (reduction).

4. **Identify the Oxidizing Agent**:
- An oxidizing agent is a substance that gets reduced while oxidizing another substance.
- Here, \(HNO_3\) is reduced (from +5 to +2), meaning it gains electrons and acts as an oxidizing agent.

5. **Evaluate the Assertion and Reason**:
- **Assertion**: \(HNO_3\) acts as an oxidizing agent. This is true.
- **Reason**: \(HNO_3\) gets oxidized to \(NO\). This is false because \(HNO_3\) is reduced to \(NO\).

6. **Conclusion**:
- The assertion is correct, but the reason is incorrect.

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