tidal energy and hydropower geothermal energy and hydropower wind energy and tidal energy geothermal energy and wind energy
I gave my students this multiple choice question: Which alternative energy resources use gravitational energy to make electricity?

Only one answer is correct among these 4 choices:
- tidal energy and hydropower
- geothermal energy and hydropower
- wind energy and tidal energy
- geothermal energy and wind energy

Could you tell me which one is correct?

tidal energy and hydropower