What is a byproduct of the light-dependent reactions?

During the light-dependent reactions of photosynthesis, which take place in the thylakoid membranes of chloroplasts, sunlight is absorbed by chlorophyll and other pigments. This energy is used to split water molecules (a process called photolysis), releasing oxygen as a byproduct. The oxygen produced is a crucial component of our atmosphere and signifies the plant's ability to convert solar energy into chemical energy.

The light-dependent reactions also produce ATP and NADPH, which are energy carriers used in the subsequent light-independent reactions (Calvin cycle) to synthesize glucose. However, the distinct production of oxygen is a key feature of the photosynthetic process, making it the correct answer when considering byproducts specifically formed during these reactions.