In environmental science, SMOG refers to a type of air pollution formed by the combination of which components?

Introduction / Context:

This question deals with atmospheric pollution. The term smog is commonly used to describe a type of polluted air that reduces visibility and can cause health problems. Understanding the origin of the term and the basic components involved helps in grasping how smog forms and why it is harmful.

Given Data / Assumptions:

• Smog is a mixture of pollutants and natural atmospheric components.
• The term historically comes from a combination of two English words.
• It often appears as a hazy or smoky layer near the ground.
• The options link smoke, fog, water vapour, fire, dust and rain in various combinations.

Concept / Approach:

The word smog is derived from smoke and fog. It originally described air pollution in industrial cities where smoke from burning coal mixed with natural fog to create a thick, unhealthy haze. Modern photochemical smog in cities with heavy traffic includes additional pollutants, but the basic term still reflects smoke like particles combining with fog or mist. The approach is to recall this word origin and match it with the correct combination.

Step-by-Step Solution:

Verification / Alternative check:

Environmental science textbooks generally define smog as a mixture of smoke and fog, especially in the historical context of industrial cities such as London in the past. Photochemical smog, common in modern cities, arises when sunlight acts on pollutants like nitrogen oxides and hydrocarbons, but it still appears as a smoky haze and continues the terminology. The etymology of the word is clearly documented as smoke plus fog, confirming this combination as the correct answer.

Why Other Options Are Wrong:

Air and water vapour describe normal atmospheric components that are present even in clean air, so they do not define a specific pollution problem. Water droplets and smoke particles describe part of the mechanism but the historical term focuses on fog rather than water alone; the best recognised phrase is smoke and fog. Fire and water vapour is not a conventional description of any atmospheric phenomenon. Dust and rain can create muddy surfaces and reduced visibility but are not the main ingredients of smog. Therefore these options do not accurately capture the meaning of smog.

Common Pitfalls:

Students sometimes confuse fog, mist and water vapour, and may think that any combination of water and some pollutant equals smog. Others may focus on modern photochemical smog and forget the original smoke plus fog origin of the term. Remembering the simple etymology of smog as smoke plus fog is an easy way to avoid mistakes in such questions.

Final Answer:

SMOG is a type of air pollution formed by the combination of Smoke and fog.