Assertion (A): `O_(3)` can act as an oxidising agent as wll as a reducing agent, but `SO_(2)` can act only as an oxidant.
Reason (R ): The oxidation number of `O` in `O_(3)` is zero, and the oxidiation number of `S` in `SO_(2)` is `+4`.

Options

A. If both `(A)` and `(R )` are correct and `(R )` is the correct explanation of `(A)`.
B. If both `(A)` and `(R )` are correct but `(R )` is not the correct explanation of `(A)`.
C. If `(A)` is correct but `(R )` is incorrect.
D. If both `(A)` and `(R )` are incorrect.

Explanation

To solve the given question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step 1: Analyze the Assertion (A)
**Assertion (A)** states that \( O_3 \) (ozone) can act as both an oxidizing agent and a reducing agent, while \( SO_2 \) (sulfur dioxide) can act only as an oxidizing agent.

1. **Ozone as an Oxidizing Agent**:
- Ozone can accept electrons and thus can oxidize other substances.
- In this case, the oxidation state of oxygen in \( O_3 \) is 0. It can be reduced to \( O^{2-} \) (where oxygen has an oxidation state of -2) or \( O^{-} \) (where oxygen has an oxidation state of -1).

2. **Ozone as a Reducing Agent**:
- Ozone can also donate electrons, meaning it can be oxidized itself.
- It can be oxidized to \( O_2 \) (where the oxidation state of oxygen is 0), thus acting as a reducing agent.

3. **Sulfur Dioxide as an Oxidizing Agent**:
- The oxidation state of sulfur in \( SO_2 \) is +4.
- \( SO_2 \) can accept electrons and be reduced to \( SO_2^{2-} \) (where sulfur has an oxidation state of +4 to -2), thus acting as an oxidizing agent.

### Conclusion for Assertion (A):
- The assertion that \( O_3 \) can act as both an oxidizing and reducing agent is **true**.
- The assertion that \( SO_2 \) can act only as an oxidizing agent is **false** because it can also act as a reducing agent.

### Step 2: Analyze the Reason (R)
**Reason (R)** states that the oxidation number of \( O \) in \( O_3 \) is zero, and the oxidation number of \( S \) in \( SO_2 \) is +4.

1. **Oxidation Number of Oxygen in \( O_3 \)**:
- In ozone (\( O_3 \)), the oxidation number of oxygen is indeed 0.

2. **Oxidation Number of Sulfur in \( SO_2 \)**:
- In sulfur dioxide (\( SO_2 \)), the oxidation number of sulfur is +4.

### Conclusion for Reason (R):
- The reason provided is **true** as the oxidation states mentioned are correct.

### Final Conclusion:
- Assertion (A) is **false** while Reason (R) is **true**. Therefore, the correct answer is that the assertion is incorrect, but the reason is correct.

### Summary:
- **Assertion (A)**: False
- **Reason (R)**: True