The correct option is B Hatch and Slack cycle
C4 plants have developed a mechanism to efficiently deliver CO2 to the RuBisCO enzyme. They utilize their specific leaf anatomy, where chloroplasts exist not only in the mesophyll cells in the outer part of their leaves but in the bundle sheath cells as well. Instead of direct fixation to RuBisCO in the Calvin cycle, CO2 is incorporated into a 4-carbon organic acid, which has the ability to regenerate CO2 in the chloroplasts of the bundle sheath cells. Bundle sheath cells can then utilize this CO2 to generate carbohydrates by the conventional C3 pathway.