Which of the following is a renewable energy source?

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

Answer: (C)

Renewable energy comes from sources that replenish naturally and won’t run out on human timescales. Solar energy fits this because sunlight is abundant and available every day. Photovoltaic cells convert sunlight directly into electricity, while solar thermal systems use heat from the sun. Because the sun’s energy is effectively inexhaustible for our purposes, solar energy is considered renewable. The other options are fossil fuels—coal, natural gas, and oil—which are finite resources formed over long periods and release greenhouse gases when burned.