Cellular respiration is a cellular process in the metabolism of sugar components to produce metabolites such as lactic acid, acetic acid, aldehydes, and other components. It starts with the cleaving of the sugar component (6-carbon) to 3-carbon components until it becomes pyruvate
B because cactus' are usually in a dry environment, they close their stomata during the day to keep water vapor from leaving the plant. Instead they do their processes at night to avoid extreme water loss.
