Concept:Hydro power is clean because it uses flowing or falling water without releasing pollutants into the environment.
Explanation:Mechanical power is obtained by burning fuel in engines, producing exhaust fumes that pollute the air.
Electrical power can cause pollution indirectly if it is generated from fossil fuels.
Chemical power may release harmful chemical substances when used on the farm.
Hydro power works by harnessing the energy of moving water.
It does not burn fuel, emit smoke, or release harmful chemicals.
Therefore, hydro power is the only option that does not cause pollution.
Answer:A. hydro