(a) Carbon dioxide and water present in the atmosphere are involved in the photosynthesis process.
(b) Oxygen gas is liberated as the by-product of the photosynthesis process.
(c) Photosynthesis is represented by an equation as follows:
6CO2 + 6H2O à C6H6O6 + 6O2
(carbon dioxide) (water) (glucose) (oxygen)