Correct Option: A

The primary acceptor of CO₂ in C₄ plants is phosphoenol pyruvate or PEP. In mesophyll cells PEP combines with CO₂ and converted into a 4 carbon compound oxaloacetic acid by PEP carboxylase. In C₃ plants, ribulose 1, 5–diphosphate is the primary acceptor of CO₂.