Q. The source of oxygen in atmosphere is due to _____:
Answer: Photosynthesis
Notes: The main source of atmospheric free oxygen is photosynthesis, which produces sugars and free oxygen from carbon dioxide and water. The organisms that carry out photosynthesis include the plant life of the land areas as well as the phytoplankton of the oceans. 6CO2 + 6H2O + energy —> C6H12O6 + 6O2

This question is part of 40000+ General Studies MCQ Series Course on GKToday Android app. Question Number: 103 in 14. Photosynthesis, Respiration and Nutrition in Plants in above course in App.