Classical smog is reducing in nature.

Answer

**Step-by-Step Solution:**

1. **Definition of Classical Smog**:
- Classical smog is defined as a mixture of smoke, fog, and sulfur dioxide. It typically occurs in urban areas where coal is burned for heating and energy.

2. **Components of Classical Smog**:
- The main components of classical smog include:
- **Smoke**: Particulate matter and various gases produced by burning fossil fuels.
- **Fog**: Water vapor that condenses in the air, forming tiny droplets.
- **Sulfur Dioxide (SO₂)**: A gas produced by the combustion of sulfur-containing fuels, such as coal.

3. **Nature of Classical Smog**:
- Classical smog is characterized as "reducing" in nature. This means that it has the ability to donate electrons in chemical reactions, thus reducing other substances.

4. **Role of Smoke in Pollution**:
- The smoke present in classical smog acts as a reducing agent. In atmospheric chemistry, reducing agents are substances that can donate electrons to other substances, leading to a reduction in their oxidation state.

5. **Conclusion**:
- Therefore, the statement "Classical smog is reducing in nature" is true. This is because the components of classical smog, particularly the smoke, contribute to its reducing properties in the atmosphere.