Which of the following is not regarded as a pollutant ?

Options

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

Answer

To determine which of the following gases is not regarded as a pollutant, we need to analyze the options provided. Let's break down the solution step by step:

### Step 1: Understand the Definition of a Pollutant
A pollutant is typically defined as a substance that, when introduced into the environment, can cause harm or adverse effects to living organisms or the ecosystem.

### Step 2: Analyze the Given Options
We need to look at the gases listed in the question (not provided here, but we will focus on carbon dioxide as per the transcript) and evaluate their roles in the environment.

### Step 3: Evaluate Carbon Dioxide
- **Role as a Pollutant**: Carbon dioxide (CO2) is released in large quantities from industrial processes, vehicle emissions, and other human activities. In excess, it contributes to air pollution and climate change, making it a pollutant in these contexts.
- **Role as a Non-Pollutant**: CO2 is also a natural component of the atmosphere. It is produced by living organisms during respiration and is utilized by plants during photosynthesis. This natural cycle is essential for life on Earth.

### Step 4: Conclusion
Given the dual role of carbon dioxide, it cannot be classified strictly as a pollutant. While it can be harmful in excessive amounts, it is also a vital gas for life processes. Therefore, among the options provided, carbon dioxide is the one that is not regarded as a pollutant in all contexts.

### Final Answer
The gas that is not regarded as a pollutant is **carbon dioxide (CO2)**.

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