In the context of energy resources, which of the following is a renewable source of energy that can be replenished naturally on a human time scale?

Introduction / Context:
Energy resources can be broadly classified into renewable and non renewable types. Renewable resources are replenished naturally and can provide energy without being permanently depleted, while non renewable resources take millions of years to form and are used up when burned as fuel. Recognising which resources are renewable is important for understanding sustainable energy policies and environmental impacts. This question asks you to identify the renewable source among several common energy resources.

Given Data / Assumptions:

• Natural gas, coal and crude oil are fossil fuels extracted from the Earth crust.
• Fossil fuels take millions of years to form from biological material under high pressure and temperature.
• Wind is produced continuously by atmospheric circulation driven by solar heating.
• Renewable resources are those that are replenished naturally on time scales relevant to human societies.

Concept / Approach:
Coal, oil and natural gas are classified as non renewable energy sources because they are formed over geological time scales from the remains of ancient plants and animals. Once extracted and burned, they cannot be quickly replaced. Their limited reserves make them non renewable. By contrast, wind energy arises from ongoing processes in the atmosphere, primarily differences in heating between land, sea and different latitudes. As long as the Sun shines and the Earth atmosphere circulates, wind will continue to blow. Harnessing wind using turbines does not reduce the overall wind resource permanently. Therefore, wind is a renewable energy source, while the fossil fuels listed are non renewable.

Step-by-Step Solution:
Step 1: Recall that non renewable resources are finite and do not regenerate on human time scales.Step 2: Identify coal as a fossil fuel formed from ancient plant matter, making it non renewable.Step 3: Recognise that crude oil is another fossil fuel derived from decayed organisms compressed over millions of years.Step 4: Note that natural gas is also a fossil fuel found with or without oil deposits and is non renewable.Step 5: Understand that wind energy comes from atmospheric motion, which is constantly regenerated by solar heating.Step 6: Conclude that wind harnessed by wind turbines is the only renewable source of energy in the given list.

Verification / Alternative check:
International energy agencies, environmental organisations and school textbooks list wind energy alongside solar, hydropower, biomass and geothermal energy as renewable sources. They repeatedly describe coal, oil and natural gas as non renewable fossil fuels responsible for significant greenhouse gas emissions. In charts showing the energy mix, the renewable category usually includes wind farms, whereas coal, oil and natural gas appear under non renewable categories. This consistent classification confirms that wind is the correct answer.

Why Other Options Are Wrong:
Natural gas is a fossil fuel that is consumed when burned; it cannot be replaced quickly, so it is non renewable. Coal is also a fossil fuel, formed over millions of years, and mining and burning it steadily reduces the amount available. Crude oil is similarly finite and, once extracted and used, cannot be regenerated on human time scales. These fuels therefore do not qualify as renewable resources.

Common Pitfalls:
Students may think that natural gas is cleaner than coal and therefore may mistakenly assume it is renewable. Cleanliness and renewability are different concepts: a resource can produce fewer pollutants but still be non renewable. Others might believe that as long as some reserves remain, the resource is renewable, which is incorrect. To avoid these errors, focus on whether the resource is naturally replenished in a short time. Wind clearly meets this condition, while fossil fuels do not.

Final Answer:
Among the options listed, wind harnessed by wind turbines is the renewable source of energy.