The source of oxygen released during photosynthesis is

Explanation

The oxygen released during photosynthesis originates from water molecules. In the light-dependent reactions, water is split into oxygen, hydrogen ions, and electrons through a process called photolysis. The oxygen is released as a byproduct and contributes to the breathable air we rely on. The other options, such as carbon dioxide, glucose, and the oxidation of chlorophyll, do not produce oxygen. Carbon dioxide is fixed into glucose in the Calvin cycle, glucose is an energy source for the plant, and chlorophyll oxidation is involved in electron transfer but not oxygen production.