photosynthesis is a source of oxygen
photosynthesis is not chemical_process. oxygenic_photosynthesis is general_photosynthesis. oxygenic_photosynthesis is not general_photosynthesis. photosynthesis is process. photosynthesis is not process. photosynthesis is chemical_process. general_photosynthesis is production. general_photosynthesis is not production. photosynthesis_in_plants is oxygenic_photosynthesis. photosynthesis_in_plants is not oxygenic_photosynthesis.