Geothermal energy is the correct answer because it is not derived from the sun. It is generated and stored within the Earth's core from the planet's original formation and the radioactive decay of minerals. In contrast, hydro-electricity, fossil fuels, and bio-mass are all indirect forms of solar energy. The sun drives the water cycle for hydro power, provided the energy for ancient plant life that became fossil fuels, and is essential for growing biomass.