Correct option is D
Explanation-
Oceans – Largest Carbon Reservoir
The oceans store more carbon than the atmosphere, soils, or plant biomass combined. About 38,000 gigatons (Gt) of carbon is stored in dissolved inorganic carbon (e.g., bicarbonate, carbonate, CO₂) and marine organisms and sediments. Oceans act as a carbon sink, absorbing ~25% of atmospheric CO₂ emitted by humans. This makes oceans the largest active reservoir in the short-term global carbon cycle.
Incorrect options -
Option a - Atmosphere
Atmosphere contains only about 750 Gt of carbon in the form of CO₂. It is important for climate regulation, but not the largest.
Option b - Plant Biomass on Land
This stores about 450-650 Gt of carbon. It includes forests, grasslands, and crops. This is vital for photosynthesis and carbon sequestration, but still much smaller than the ocean.
Option c - Soils
Soil store more than plants and air, around 1,500–2,400 Gt of carbon. This is significant reservoir, especially in organic matter and permafrost, but still less than the oceans.
Final Answer: Option d – The Ocean
