Answer is: c) CAM.
CAM (crassulacean acid metabolism) is a carbon fixation pathway.
In plants with CAM carbon fixation, carbon dioxide is stored as the malic acid malate in vacuoles at night.
During the daytime, the malic acid is transported to chloroplasts where it is converted back to carbon dioxide, which is then used during photosynthesis.
Malic acid is an organic dicarboxylic acid with the molecular formula C₄H₆O₅.
