The smog is essentially caused by the presence of

Types of Smog

The term "smog" is a combination of the words "smoke" and "fog." Atmospheric smog primarily manifests in two distinct forms, both heavily driven by gaseous pollution:

• Classical (London) Smog: Occurs in cool, humid climates. It is a reducing mixture caused by the heavy combustion of sulfur-bearing fossil fuels, which releases large amounts of oxides of sulfur ($$\text{SO}_x$$) and particulate matter into the atmosphere.
• Photochemical (Los Angeles) Smog: Occurs in warm, dry, and sunny climates. It is an oxidizing mixture that forms when solar radiation triggers chemical reactions between unburnt hydrocarbons and oxides of nitrogen ($$\text{NO}_x$$), producing secondary pollutants like ozone ($$\text{O}_3$$) and PAN.

Component Analysis:

Looking at the fundamental building blocks of ambient air pollution, the primary components that initiate the production of both types of smog are industrial and vehicular emissions:

1. Sulfur Dioxide ($$\text{SO}_2$$): Catalyzed in the atmosphere to form acid mists and classical reducing smog.
2. Nitrogen Oxides ($$\text{NO}$$ and $$\text{NO}_2$$): Absorb sunlight to initiate the free radical chain reactions that generate photochemical smog.

In contrast, diatomic oxygen ($$\text{O}_2$$) and diatomic nitrogen ($$\text{N}_2$$) are the standard, non-toxic constituents of clean air, and ozone ($$\text{O}_3$$) is a secondary byproduct rather than the original root cause emissions.

Conclusion:

The core components that essentially cause and sustain smog formation in our atmosphere are the gaseous oxides of sulfur and nitrogen.

Answer: Option C — Oxides of sulphur and nitrogen