Which of the following acts as a pollutant ?

Options

A. CO
B. `SO_(2)`
C. `CO_(2)`
D. `O_(2)`

Answer

To determine which of the given options acts as a pollutant, we need to understand what a pollutant is and analyze the options provided.

### Step-by-Step Solution:

1. **Define a Pollutant**:
A pollutant is defined as any substance or energy introduced into the environment that has harmful effects on living organisms or the environment itself.

2. **Identify the Options**:
Let's assume the options provided are A, B, C, and D, where each option represents a different substance. For this explanation, we will consider Carbon Monoxide (CO), Sulfur Dioxide (SO2), Carbon Dioxide (CO2), and Oxygen (O2) as potential options.

3. **Analyze Each Substance**:
- **Carbon Monoxide (CO)**: This is a colorless, tasteless gas that is produced during the incomplete combustion of carbon-containing fuels such as oil and coal. It is known to be a harmful air pollutant.
- **Sulfur Dioxide (SO2)**: This is a gas produced by volcanic eruptions and industrial processes, particularly the burning of fossil fuels. It can cause acid rain but is not always classified as a pollutant in the same way as CO.
- **Carbon Dioxide (CO2)**: This is a naturally occurring gas that is a byproduct of respiration and combustion. While it contributes to greenhouse gas effects, it is not classified as a pollutant in the traditional sense.
- **Oxygen (O2)**: This is essential for life and is not considered a pollutant.

4. **Conclusion**:
Based on the analysis, Carbon Monoxide (CO) is the only substance among the options that acts as a pollutant due to its harmful effects on health and the environment.

### Final Answer:
The correct option that acts as a pollutant is **A: Carbon Monoxide (CO)**.