Conventional Energy Resources

Correct answer: A. Non-renewable resource

The governing concept is the classification of energy resources according to the time required for replacement. Coal is a fossil fuel formed from buried plant remains that were transformed by heat and pressure over millions of years. Because this geological process is extremely slow compared with human consumption, coal deposits cannot be replenished within a human lifetime. Its reserves are also finite, so coal is a non-renewable resource and option A is correct. Solar radiation, wind, and flowing water are renewable because natural processes continually restore them. Option B is therefore incorrect. Coal is not unlimited, and it is a naturally occurring mineral fuel rather than a human-made resource, so options C and D are also incorrect.

Correct answer: A. Flowing or falling water

Hydroelectricity is produced by converting the energy of water into electrical energy. Water stored at a height has potential energy, and water moving through a channel has kinetic energy. When the water flows or falls through turbines, it rotates them; the generator then converts this mechanical motion into electricity. Thus, option A is correct because flowing or falling water is the direct energy resource used in hydropower. Dry sand and sea salt do not drive turbines, while coal ash is a residue rather than the water resource used in this process. Hydropower is generally classified as a renewable energy source when water cycles are maintained.