Correct Answer: Tidal energy

Solution : The correct answer is (D) Tidal energy

Tidal energy is considered a non-conventional or alternative energy source. Non-conventional energy sources, also known as alternative or renewable energy sources, are those that are different from conventional fossil fuels (such as coal, oil, and natural gas) and are typically more environmentally friendly and sustainable.

Tidal energy harnesses the energy from the tides, which are driven by the gravitational forces of the moon and the sun. Tidal energy is renewable and considered a non-conventional energy source, as it has minimal environmental impact and is not dependent on fossil fuel resources.