The smog is essentially caused by the presence of

Options

A. `O_(2)` and `O_(3)`
B. `O_(2)` and `N_(2)`
C. Oxides of sulphur and nitrogen
D. `O_(3)` and `N_(2)`

Answer

**Step-by-Step Solution:**

1. **Understanding Smog**: Smog is a type of air pollution that is characterized by a mixture of smoke and fog. It is typically seen in urban areas and can have serious health effects.

2. **Components of Smog**: The primary components that contribute to the formation of smog include sulfur oxides (SOx) and nitrogen oxides (NOx). These compounds are released into the atmosphere from various sources, including vehicle emissions, industrial processes, and burning of fossil fuels.

3. **Role of Sunlight**: The presence of sunlight is crucial in the formation of smog. Sunlight initiates photochemical reactions that lead to the transformation of these oxides into secondary pollutants.

4. **Chemical Reactions**:
- Nitrogen dioxide (NO2) reacts with sunlight (Hν) to produce nitric oxide (NO) and nascent oxygen (O).
- The nascent oxygen then reacts with molecular oxygen (O2) to form ozone (O3).
- Ozone can further react with nitrogen monoxide (NO) to regenerate nitrogen dioxide (NO2) and produce oxygen (O2).
- Hydrocarbons present in the atmosphere can react with nascent oxygen to form reactive radicals, which can lead to the formation of peroxyacetyl nitrate (PAN).

5. **Conclusion**: The presence of sulfur oxides and nitrogen oxides, particularly in the presence of sunlight, is what primarily causes smog. Therefore, the answer to the question is that smog is essentially caused by the presence of oxides of sulfur and nitrogen.

**Final Answer**: Smog is essentially caused by the presence of oxides of sulfur and nitrogen.

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