The correct answer is option B - Photosynthesis
The green structure labelled X in the plant cell picture is where photosynthesis occurs, the process of converting sunlight, carbon dioxide, and water into glucose and oxygen.
Photosynthesis allows plants to use the energy from sunlight to convert carbon dioxide and water into glucose, a carbohydrate, and oxygen. In general, photosynthesis occurs in the mesophyll layer of plant leaves, where a specialized structure called the chloroplast contains pigments such as chlorophyll that capture sunlight.
Cellular respiration is another vital process, which uses oxygen to convert glucose into energy that cells can use, releasing carbon dioxide and water as byproducts. However, the green structure mentioned in the question is associated with photosynthesis rather than respiration.
In summary, the correct answer to the question about the process taking place at label X is photosynthesis.