In environmental science, which of the following describes the main beneficial role that ozone in the atmosphere plays for life on Earth?

Introduction / Context:
Ozone is a form of oxygen present in small quantities in the Earth atmosphere. This question tests your understanding of why ozone, especially in the stratosphere, is considered protective and beneficial for living organisms. Many people hear about the ozone layer and its depletion in environmental news, so knowing its main role is important for general science and competitive exams.

Given Data / Assumptions:

• Ozone (O3) exists in a layer high above the Earth surface, mainly in the stratosphere.
• The question asks specifically for the main benefit of ozone, not every possible effect.
• Several possible environmental roles are listed, including absorbing radiation and reducing pollution.

Concept / Approach:
The ozone layer in the stratosphere acts as a natural shield by absorbing a large portion of the Sun harmful ultraviolet (UV) radiation, especially UV-B rays. Excessive UV radiation can damage DNA, increase skin cancer risk, harm eyes, and reduce crop yields and marine productivity. Therefore, the primary benefit of ozone is its role in screening out harmful UV radiation. While ozone at ground level can act as a pollutant and participate in complex chemical reactions, it is not the main agent for neutralising carbon monoxide, filtering particulates, or directly removing all air pollutants. These other tasks are handled by different atmospheric processes, chemical reactions, and pollution control measures, not mainly by ozone itself.

Step-by-Step Solution:

Verification / Alternative check:
Environmental science textbooks and reports from international agencies describe the ozone layer as essential for protecting living organisms from harmful ultraviolet radiation. They explain that without this layer, UV radiation at the Earth surface would be much higher, increasing skin cancer, cataracts, and ecological damage. They also distinguish between stratospheric ozone (good ozone) and tropospheric ozone (bad ozone that contributes to smog). None of these references describe ozone as the main remover of carbon monoxide or particulates, confirming that the correct answer must highlight UV absorption as the key benefit.

Why Other Options Are Wrong:

It neutralises the toxic effects of carbon monoxide in the lower atmosphere is wrong because carbon monoxide is mainly removed by oxidation and mixing processes, not directly neutralised by ozone acting as a primary cleanser.

It directly reduces all types of air pollution over cities is incorrect because ozone itself can become a harmful component of photochemical smog at ground level, and it does not simply remove all pollution.

It filters dust and smoke particulates out of the atmosphere is wrong because solid and liquid particles are removed mainly by gravity, rain, and filtration technologies, not by chemical reaction with ozone.

Common Pitfalls:
Students sometimes mix up the roles of various atmospheric components and think that any “good” gas cleans up all pollution. Another common confusion is between stratospheric ozone, which protects life, and ground level ozone, which can be harmful. To avoid these mistakes, remember that the main beneficial role of the ozone layer is to absorb harmful ultraviolet radiation from the Sun, reducing the amount that reaches the Earth surface and protecting living organisms.