Oxygen present in the atmosphere has been formed by?
A. Evaporation of sea water
B. Photosynthesis by plants
C. Putrfaction of animals and plants
D. Metabolism of micro-organisms
Answer:B
Oxygen present in the atmosphere has been formed by?
A. Evaporation of sea water B. Photosynthesis by plants C. Putrfaction of animals and plants D. Metabolism of micro-organisms