Which gas is produced as a byproduct of photosynthesis?

• A. Carbon dioxide
• B. Nitrogen
• C. Hydrogen
• D. Oxygen

Answer: (D)

In photosynthesis, light energy drives the capture of carbon dioxide and water to make glucose, and during the light-dependent reactions water is split to provide electrons. This splitting releases oxygen gas as a byproduct, which exits the leaf through the stomata. So the gas produced as a byproduct is oxygen. Carbon dioxide is used up, not released, and nitrogen gas isn’t a product of this process.