Which can act as a reducing agent ?

Options

A. CO
B. `CO_(2)`
C. `SnO_(2)`
D. `PbO_(2)`

Explanation

To determine which substance can act as a reducing agent among carbon monoxide, carbon dioxide, tin dioxide, and lead dioxide, we need to understand the definition and characteristics of a reducing agent.

### Step-by-Step Solution:

1. **Understanding Reducing Agents**:
A reducing agent is a substance that can donate electrons to another species, thereby reducing that species. In the process, the reducing agent itself gets oxidized.

2. **Analyzing Each Option**:
- **Carbon Monoxide (CO)**:
Carbon monoxide has a lone pair of electrons on the carbon atom. It can donate this electron pair to electron-deficient species (like metal ions), thus acting as a reducing agent. For example, it can reduce zinc oxide (ZnO) to zinc (Zn) while itself being oxidized to carbon dioxide (CO2).
- **Carbon Dioxide (CO2)**:
Carbon dioxide is already in a fully oxidized state and does not have the ability to donate electrons. Therefore, it cannot act as a reducing agent.
- **Tin Dioxide (SnO2)**:
Tin dioxide is also in a higher oxidation state and does not have the capacity to donate electrons. It typically acts as an oxidizing agent rather than a reducing agent.
- **Lead Dioxide (PbO2)**:
Similar to tin dioxide, lead dioxide is in a high oxidation state and does not have the ability to donate electrons. It also acts as an oxidizing agent.

3. **Conclusion**:
Based on the analysis, the only substance that can act as a reducing agent among the given options is **Carbon Monoxide (CO)**.

### Final Answer:
**Carbon Monoxide (CO)** can act as a reducing agent.

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