Photosynthesis in C4-plants is relatively less limited by atmospheric CO2 levels because
The correct option is D)
Plants such as sugarcane and sorghum fix atmospheric carbon dioxide into phosphoenol pyruvic acid to produce oxaloacetic acid (a four-carbon acid) in the presence of phosphoenolpyruvate carboxylase (PEP carboxylase). Such plants are called C4 plants. In C4 plants, the primary product of OAA is mediated by PEP carboxylase, so it is relatively less limited by atmospheric CO2 levels.
So, the correct answer is 'The primary fixation of CO2 is mediated via PEP carboxylase'.