Compressed Natural Gas (CNG) is considered a cleaner fuel for which of the following reasons about its emissions and impact on the environment?

Introduction / Context:
This question comes from environmental science and energy resources. It focuses on why compressed natural gas, commonly called CNG, is described as a cleaner fuel compared to conventional petrol and diesel. Understanding this helps students connect fuel choice with air pollution and climate change.

Given Data / Assumptions:

• Statement I: CNG produces oxides of sulphur and nitrogen in very small amounts.
• Statement II: CNG makes the environment less polluted.
• Statement III: CNG emits less greenhouse gases.
• The task is to decide which combination of statements correctly explains why CNG is cleaner.

Concept / Approach:
CNG is mainly methane. When it burns completely, it produces carbon dioxide and water, with significantly lower emissions of sulphur oxides, nitrogen oxides, and particulate matter compared with diesel and some types of petrol. Lower emissions of these pollutants mean reduced smog and acid rain potential, and the smaller emission of greenhouse gases per unit of energy makes it relatively better for the climate. Therefore, each statement that describes lower pollution and lower greenhouse gas emission is likely to be correct.

Step-by-Step Solution:

Verification / Alternative check:
Many environmental science sources and government policies encourage using CNG for urban transport because of reduced emissions of sulphur oxides, nitrogen oxides, carbon monoxide, and particulate matter. This is reflected in the introduction of CNG buses and taxis in several cities. These facts support the idea that all three given statements contribute to CNG being called a cleaner fuel.

Why Other Options Are Wrong:

• Option a is wrong because it leaves out statement III, even though lower greenhouse gas emission is an important reason for calling CNG greener.
• Option b is wrong because it ignores statement I, which is about low levels of sulphur and nitrogen oxides that directly reduce air pollution.
• Option c is wrong because it excludes statement II, even though reduced local pollution is a widely recognised benefit of CNG.

Common Pitfalls:
Some learners may overthink the exact chemical details and worry about minor exceptions, leading them to reject one of the statements. At the school level, however, the key idea is that CNG burns more cleanly, produces fewer harmful pollutants, and relatively less greenhouse gas per unit of energy than many other fossil fuels. As long as a statement captures these broad advantages, it can be treated as correct for this type of exam.

Final Answer:
All I, II and III