Answer:
Electrolysis is more expensive. Electrolysis is when water molecules break down into oxygen and hydrogen gas. Breakdown of methane contains carbon and releases CO2.
Photochemical smog results from automobile pollutants reacting with ultraviolet light from the sun. <span>Nitrogen oxides released from the automobile are introduced into the atmosphere reacts with sunlight to produce singular oxygen atoms. Oxygen atoms then combine with molecular oxygen to produce ozone which is one of the components of photochemical smog.</span>
I believe it's stem cells.