During photosynthesis, plants remove carbon dioxide from the air and release which gas?

• A. Nitrogen
• B. Oxygen
• C. Methane
• D. Hydrogen

Answer: (B)

When light powers photosynthesis, water molecules are split during the light-dependent reactions. This photolysis releases electrons, protons, and molecular oxygen. The oxygen atoms pair to form O2, which exits the leaf as a gas, while the electrons and protons drive the synthesis of sugars from carbon dioxide in the later stages. The overall process shows water and carbon dioxide yielding glucose and oxygen, with the released gas coming from the water rather than the carbon dioxide. The other gases listed aren’t produced in this process: plants don’t release nitrogen as part of photosynthesis, methane is produced by certain microbes under specific conditions, and hydrogen gas isn’t a typical byproduct of plant photosynthesis. Oxygen is the gas released.