A process of CO₂ fixation in photosynthesis by which the first product is the four-carbon oxaloacetate molecule is called:

Explanation

The correct answer is C4 photosynthesis. In C4 photosynthesis, carbon dioxide is initially fixed into a four-carbon compound, oxaloacetate, which is an adaptation to minimize photorespiration and increase efficiency under specific environmental conditions. This process occurs in plants like maize and sugarcane, where the fixation happens in mesophyll cells and is then transferred to bundle sheath cells where the Calvin cycle takes place.C3 photosynthesis is incorrect because it involves the direct fixation of CO₂ into a three-carbon compound, not oxaloacetate.The light reaction is incorrect, as it deals with the conversion of light energy into chemical energy without involving carbon fixation.Cyclic electron flow is incorrect because it focuses on electron transport in the light-dependent reactions and does not relate to the carbon fixation process.