Answer: photosynthesis
Explanation: In photosynthesis, carbon dioxide and water reacts in the presence of sunlight to produce glucose and oxygen. In photosynthesis, oxygen is released in to the atmosphere while the glucose formed is stored in the plant as food. No carbon is introduced in to the atmosphere during respiration rather carbon dioxide is used up.
In respiration, glucose is broken down in the presence of oxygen to produce carbon dioxide, water and energy. Carbon is introduced in to the atmosphere in form of carbon dioxide.
In forest fires and burning of fossil fuels, wood and fuels burn in sufficient supply of oxygen liberates carbon dioxide (CO2) but when it burns in insufficient supply of oxygen, it liberates carbon monoxide (CO). In both cases carbon is introduced in to the atmosphere in form of carbon dioxide or carbon monoxide.
