Explanation

Carboxylation (In $C_{3}$-cycle) It is the fixation of $CO_{2}$ into a stable organic intermediate. Carboxylation is the most crucial step of the Calvin cycle, where $CO_{2}$ is utilised for the carboxylation of RuBP. This reaction is catalysed by the enzyme RuBP carboxylase, which results in the formation of two molecules of 3-PGA. Since, this enzyme also has an oxygenation activity. It would be more correct to call it RuBP carboxylase-oxygenase or RuBisCo