A. Nitrogen cycle
B. Green Plants
C. Water
D. Carbon Cycle
✅ The correct answer is option B.
The main source of atmospheric free oxygen is photosynthesis, which produces sugars and free oxygen from carbon dioxide and water. Hence, answer B is correct.
The main source of atmospheric free oxygen is photosynthesis, which produces sugars and free oxygen from carbon dioxide and water. Hence, answer B is correct.