Final answer:
The process that forms oxygen from carbon dioxide is photosynthesis, while respiration forms carbon dioxide from oxygen. Option a. photosynthesis, respiration is the correct answer to the question.
Step-by-step explanation:
The correct answer to the student's question is: Oxygen is formed from carbon dioxide in photosynthesis, while carbon dioxide is formed from oxygen in respiration. Therefore, the correct option is a. photosynthesis, respiration. During the process of photosynthesis, plants absorb carbon dioxide (CO₂) and water (H₂O) and use the energy from sunlight to convert these into glucose (C₆H₁₂O₆) and oxygen (O₂). Conversely, in respiration, cells use oxygen to break down glucose, releasing energy, water, and carbon dioxide as byproducts.