There are various ways on how gases enter and leave plants and so as photosynthesis. Photosynthesis has many alternative pathways. one most common pathway is the CAM pathway. This pathway is being used by pineapples and cactus. Plants that use this pathway have their stomata open at night and closed at daytime. During night time, these plants take in carbon dioxide which are fixed into organic compounds. At daytime, the carbon dioxide is being released from the organic compounds then enters the Calvin Cycle. The answer to this question then is letter C. In a Cactus, carbon is only fixed during the night.
