The oxidant which cannot act as a reducing agent is

Options

A. `SO_(2)`
B. `NO_(2)`
C. `CO_(2)`
D. `ClO_(2)`

Explanation

To determine which oxidant cannot act as a reducing agent, we need to analyze the oxidation states of the elements in the given compounds and see if they can be oxidized further.

### Step-by-Step Solution:

1. **Understanding Oxidation and Reduction**:
- An oxidizing agent (or oxidant) is a substance that gains electrons and is reduced in a chemical reaction.
- A reducing agent is a substance that loses electrons and is oxidized.

2. **Analyzing SO2 (Sulfur Dioxide)**:
- In SO2, sulfur has an oxidation state of +4.
- It can be oxidized to +6 (for example, to SO3).
- Therefore, SO2 can act as a reducing agent.

3. **Analyzing NO2 (Nitrogen Dioxide)**:
- In NO2, nitrogen has an oxidation state of +4.
- It can be oxidized to +5 (for example, to N2O5).
- Thus, NO2 can also act as a reducing agent.

4. **Analyzing CO2 (Carbon Dioxide)**:
- In CO2, carbon has an oxidation state of +4.
- This is the maximum oxidation state for carbon; it cannot be oxidized further.
- Therefore, CO2 cannot act as a reducing agent.

5. **Analyzing ClO2 (Chlorine Dioxide)**:
- In ClO2, chlorine has an oxidation state of +4.
- It can be oxidized to +7 (for example, to ClO3).
- Hence, ClO2 can act as a reducing agent.

6. **Conclusion**:
- Among the compounds analyzed, CO2 is the only one that cannot be oxidized further and thus cannot act as a reducing agent.

### Final Answer:
The oxidant which cannot act as a reducing agent is **CO2 (Carbon Dioxide)**.