Which of the following is a renewable energy resource?

• A. Coal
• B. Natural gas
• C. Nuclear
• D. Solar energy

Answer: (D)

Renewable energy resources are those that can be replenished naturally in a human lifetime. Solar energy fits this because the sun provides a continuous, virtually inexhaustible source of energy; we can capture and convert sunlight into electricity or heat without depleting the source on human timescales. Fossil fuels like coal and natural gas come from ancient organic matter and form over millions of years, so once burned they are effectively depleted and cannot be reassembled quickly. Nuclear energy relies on uranium, which is finite, and it also produces long-lived waste rather than being replenished on relevant timescales. So solar energy stands out as renewable due to its source being continuously available and naturally replenished, even though its daily generation can vary and may require storage or grid integration to maintain steady supply.