What gas is produced by plants during photosynthesis and consumed by animals during respiration?

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

Answer: (C)

Oxygen is produced by plants during photosynthesis and is what animals rely on during respiration to release energy from food.

During photosynthesis, plants use sunlight to split water molecules, releasing oxygen gas as a byproduct into the air. Animals breathe in that oxygen and use it in cellular respiration to break down sugars for energy, which releases carbon dioxide and water as wastes. That makes oxygen the gas that fits both parts of the question.

Nitrogen isn’t a direct product of photosynthesis, and while carbon dioxide is involved in photosynthesis (it’s taken in), it’s not the gas produced by plants and consumed by animals in respiration. Hydrogen gas isn’t a primary gas involved in this basic plant–animal gas exchange.