Which substances are fossil fuels?

• A. Coal, oil, natural gas
• B. Uranium, thorium, plutonium
• C. Wood, peat, charcoal
• D. Solar, wind, hydro

Answer: (A)

Fossil fuels are energy-rich carbon-based substances formed from ancient organic matter that was buried and transformed by heat and pressure over long timescales, storing the energy originally captured from the sun by plants. The main examples people rely on are coal, oil, and natural gas, which come from different geological conditions but share that origin and are nonrenewable. The other options don’t fit: uranium, thorium, and plutonium are nuclear fuels used in reactors, not fossil fuels formed from ancient organic material. Wood and charcoal come from recent plant material, while peat is an early-stage plant matter not typically classified with the long-term geological transformation of true fossil fuels. Solar, wind, and hydro are energy sources that come from natural processes rather than from burning fuels.