Answer : Option C

Explanation :

The unusually high concentration of oxygen gas on Earth is the result of the oxygen cycle. This biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for modern Earth’s atmosphere. Photosynthesis releases oxygen into the atmosphere, while respiration and decay remove it from the atmosphere. In the present equilibrium, production and consumption occur at the same rate of roughly 1/2000th of the entire atmospheric oxygen per year. Free oxygen also occurs in solution in the world’s water bodies. The increased solubility of O₂ at lower temperatures has important implications for ocean life, as polar oceans support a much higher density of life due to their higher oxygen content.