Pollution is not caused by:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Hydroelectric power plant
A hydroelectric power plant turns the energy of falling water into electricity. It burns no fuel and produces no smoke, ash or radioactive waste, so it does not pollute the air or water while it runs.
Why the other options are incorrect
Option (1) Radioactive power plant — Incorrect. A nuclear plant leaves radioactive waste and releases heated water into rivers or the sea.
Option (3) Thermal power plant — Incorrect. Burning coal releases smoke, fly ash, sulphur dioxide and carbon dioxide.
Option (4) Automobile — Incorrect. Vehicles burning petrol or diesel give out exhaust gases such as carbon monoxide and oxides of nitrogen.