Which of these is a non-renewable energy source?

**The reasoning** A **non-renewable** energy source is one that cannot be replaced within a human lifetime — once you use it up, it's gone. Coal is formed from ancient plants that were buried and compressed over **millions of years**. When we burn coal for energy, we're depleting reserves that took geological ages to form. We can't make more coal in any practical timeframe. In contrast, solar, wind, and geothermal are **renewable** because they regenerate naturally and continuously. The sun shines every day, wind keeps blowing, and Earth's internal heat persists for billions of years. **Why the wrong options tempt you** - **A & B (Solar/Wind):** You might forget that these are *naturally replenished* daily. They never "run out." - **D (Geothermal):** This one tricks students! Though it uses heat from deep underground, that heat is continuously produced by Earth's core and will last billions of years — making it renewable on human timescales. **Quick takeaway** If it took **millions of years to form** (like fossil fuels: coal, oil, gas), it's non-renewable; if nature **replaces it continuously**, it's renewable.