There is a pressing need to use non-conventional energy sources because:
Therefore, renewable sources like solar, wind, tidal and biomass energy must be promoted.
Source: Conservation of Energy Resources / Non-Conventional Sources of Energy, Chapter 5
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Examiners expect two or three distinct reasons for this 2-mark question. The key points are: (1) fossil fuels are finite and depleting, (2) rising prices/energy insecurity, and (3) environmental damage. You don't need all three — any two well-stated points earn full marks. Avoid writing a lengthy essay; crisp, numbered points work best here.