Annual carbon fixation by photosynthesis is

Answer: Option A

Annual carbon fixation by photosynthesis is 7 × 10¹³.
The primary form of inorganic carbon that is fixed is carbon dioxide (CO₂). It is estimated that approximately 258 billion tons of carbon dioxide are converted by photosynthesis annually.
The majority of the fixation occurs in terrestrial environments, especially the tropics. The gross amount of carbon dioxide fixed is much larger since approximately 40% is consumed by respiration following photosynthesis.