Which of the following are byproducts of the light reactions of photosynthesis?

The light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts and are primarily responsible for converting solar energy into chemical energy, which is then used to fuel the Calvin cycle. During these reactions, light energy is absorbed by chlorophyll and other pigments, leading to the splitting of water molecules (photolysis) in a process that produces oxygen gas as a byproduct.

Alongside oxygen, the light reactions also generate ATP and NADPH, which are essential energy carriers for the subsequent dark reactions (Calvin cycle). Therefore, the presence of both oxygen and ATP as products of the light reactions confirms their roles in converting solar energy into forms that can be used for the synthesis of glucose in the later stages of photosynthesis.

In summary, the correct answer cites oxygen and ATP because these are indeed the significant byproducts produced during the light reactions, facilitating the whole photosynthetic process.