Which one of these causes of air pollution releases particulate matter into the air?

Options

A. Vehicular emissions
B. Volcanic eruptions
C. Burning of coal
D. Grass fires

Explanation

To determine which cause of air pollution releases particulate matter into the air, we can follow these steps:

### Step 1: Understand Particulate Matter
Particulate matter (PM) refers to tiny particles or droplets in the air that can be harmful to health. They can be classified into primary and secondary particulate matter.

### Step 2: Identify Primary vs. Secondary Particulate Matter
- **Primary Particulate Matter**: This is emitted directly into the air from a source. Examples include smoke from fires and dust.
- **Secondary Particulate Matter**: This forms in the atmosphere through chemical reactions involving gases. Examples include particulate matter formed from vehicular emissions and burning coal.

### Step 3: Analyze the Options
To answer the question, we need to evaluate the options given:
1. **Grass Fires**: These produce particulate matter directly through combustion without any chemical reactions.
2. **Vehicular Emission**: This involves chemical reactions that create secondary particulate matter.
3. **Volcanic Eruption**: This also involves chemical reactions and produces secondary particulate matter.
4. **Burning Coal**: This produces secondary particulate matter due to chemical reactions.

### Step 4: Conclusion
Among the options, **grass fires** are the only source that releases primary particulate matter directly into the air without undergoing chemical reactions. Therefore, the correct answer is **grass fires**.

### Final Answer
Grass fires cause air pollution by releasing particulate matter directly into the air.

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