Photosynthesis uses all of the following except _____ to make food.

• A. oxygen
• B. water
• C. carbon dioxide
• D. sunlight

Answer: (A)

Verified step by step guidance

1. Step 1: Begin by understanding the process of photosynthesis. Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. This process primarily occurs in the chloroplasts of plant cells.
2. Step 2: Identify the key reactants involved in photosynthesis. The main inputs for photosynthesis are water (H₂O), carbon dioxide (CO₂), and sunlight. These are essential for the light-dependent and light-independent reactions.
3. Step 3: Recall the chemical equation for photosynthesis: $6_{\mathrm{CO}}{2}_{}+6_H{2}_{}O\to C_6{H}_{\mathrm{12}}{O}_6+6_O{2}_{}$. This equation shows that oxygen is a byproduct, not a reactant.
4. Step 4: Analyze the options provided in the question. Water, carbon dioxide, and sunlight are all necessary for photosynthesis to occur. Oxygen, however, is produced during the process and is not used as an input.
5. Step 5: Conclude that the correct answer is 'oxygen,' as it is not required as a reactant in photosynthesis but is instead released as a byproduct during the light-dependent reactions.