Explanation

$CO_{2}$ assimilation during photosynthesis generally takes place in two ways in plants (i) $\mathbf{C}_{\mathbf{3}}$ pathway Those plants in which the first product of $CO_{2}$ fixation is a $C_{3}$ acid (PGA), i.e., the $C_{3}$ pathway (ii) $\mathbf{C}_{\mathbf{4}}$ pathway Those plants in which the first product $C_{4}$ acid (OAA), i.e., the $C_{4}$ pathway