Which are necessary for photosynthesis to occur?

• A. Oxygen, Light energy, and Carbon dioxide
• B. Light energy, nitrogen, and Carbon dioxide
• C. Light energy, Water, and Carbon dioxide
• D. Light energy only

Answer: (C)

Photosynthesis needs energy from light to drive the chemical changes, and it uses water and carbon dioxide as the raw materials to build sugar. In the chloroplasts, light energy powers the reactions that split water, providing electrons and hydrogen; this splitting also releases oxygen as a byproduct. Carbon dioxide supplies the carbon atoms to form glucose, the sugar plants store as food. If any of these inputs are missing, the process can’t proceed. Oxygen is produced, not required as an input, and nitrogen isn’t involved in this main process. So the combination of light energy, water, and carbon dioxide is essential for photosynthesis.