Many cactus plants, such as the species shown in the illustration, use a special type of photosynthesis called cam photosynthesis. this specialized process allows the cactus plant to keep the stoma or leaf openings closed during the day. most other plant species keep their stoma open during daylight hours. which is the most likely reason that cactus use this special photosynthetic process? a) retain oxygen b) conserve water c) avoid insect predators d) conserve energy in the form of atp