Which of the following is a byproduct of photosynthesis?

In photosynthesis, plants convert carbon dioxide and water into glucose and oxygen, using sunlight as energy. Among the products of this process, oxygen is released as a byproduct, which is essential for the survival of most living organisms on Earth. This oxygen is produced in the chloroplasts during the light-dependent reactions of photosynthesis, where water molecules are split, releasing oxygen into the atmosphere.

Water vapor, carbon dioxide, and glucose are involved in the process but are not considered byproducts in the same way as oxygen. Water vapor is part of the environment that can be utilized during photosynthesis, carbon dioxide is a raw material consumed in the reaction, and glucose is the primary product that serves as energy for the plant. Therefore, oxygen is the correct answer as it is the key byproduct that is released into the air.