A secondary pollutant is

Options

A. `O_(3)`
B. CO
C. `CH_(4)`
D. Pb.

Answer

To determine which of the given options is a secondary pollutant, we can follow these steps:

### Step 1: Understand the Definition of Secondary Pollutants
Secondary pollutants are not directly emitted into the atmosphere. Instead, they are formed through chemical reactions between primary pollutants and other substances in the atmosphere.

### Step 2: Identify the Given Options
The options provided are:
- O3 (Ozone)
- CO (Carbon Monoxide)
- CH4 (Methane)
- PB (Lead)

### Step 3: Analyze Each Option
- **O3 (Ozone)**: Ozone is formed when primary pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. Therefore, ozone is a secondary pollutant.

- **CO (Carbon Monoxide)**: Carbon monoxide is a primary pollutant that is emitted directly from sources like vehicle exhaust and industrial processes.

- **CH4 (Methane)**: Methane is also a primary pollutant, primarily released from natural sources and human activities such as agriculture and fossil fuel extraction.

- **PB (Lead)**: Lead is a primary pollutant that is emitted directly from sources such as industrial processes and the burning of fossil fuels.

### Step 4: Conclusion
Based on the analysis, the only secondary pollutant among the options is **O3 (Ozone)**.

### Final Answer
A secondary pollutant is **O3 (Ozone)**.

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