Which of the following is a renewable energy source?

• A. Fossil fuels
• B. Coal
• C. Geothermal
• D. Oil

Answer: (C)

Renewable energy sources are those that can be replenished naturally and used sustainably over time. Geothermal taps into heat from inside the Earth, which is continuously produced by natural processes, so this heat can be harnessed repeatedly to generate power or provide heating without running out on human timescales. Fossil fuels like coal and oil come from ancient organic matter and are finite; once burned, they are not quickly replenished, so they’re not considered renewable. That’s why geothermal is the renewable option here.