Which statement about renewable energy sources is accurate?

• A. The renewable energy sources replenish naturally only after millions of years.
• B. Nonrenewable energy sources replenish naturally within decades.
• C. Renewable energy sources replenish naturally on human timescales.
• D. All energy sources are equally limited and polluting.

Answer: (C)

Renewable energy sources replenish naturally on human timescales. This means we can rely on them repeatedly within our lifetimes because their supply is continually regenerated by natural processes. The sun delivers energy every day, wind keeps occurring as air moves, water cycles keep rivers and tides flowing, and biomass can regrow after harvest in a few years. These resources don’t disappear after use the way fossil fuels do, which formed over millions of years and are not replenished on our timescales. By contrast, nonrenewable sources are finite and take geological ages to form, so they aren’t replenished within decades. Also, not all energy sources are equally limited or polluting; some renewables provide energy with little or no emissions during operation, while others have environmental trade-offs in production or land use. So the statement that renewable energy sources replenish naturally on human timescales accurately captures how these resources behave in our world.