In the process of photosynthesis, what is the primary source of the oxygen gas (O_2) released by plants?

• A. Carbon dioxide (CO_2)
• B. Chlorophyll
• C. Water (H_2O)
• D. Glucose (C_6H_{12}O_6)

Answer: (C)

Verified step by step guidance

1. Understand the process of photosynthesis: Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose and oxygen as byproducts. It occurs in two main stages: the light-dependent reactions and the Calvin cycle.
2. Focus on the light-dependent reactions: During these reactions, light energy is absorbed by chlorophyll and other pigments in the thylakoid membranes of chloroplasts. This energy is used to split water molecules (H₂O) in a process called photolysis.
3. Break down photolysis: Photolysis involves the splitting of water molecules into oxygen gas (O₂), protons (H⁺), and electrons. The oxygen gas is released as a byproduct into the atmosphere, while the protons and electrons are used in subsequent steps of photosynthesis.
4. Clarify the role of water (H₂O): Water is the primary source of the oxygen gas (O₂) released during photosynthesis. The oxygen atoms in water molecules are liberated during photolysis and combine to form O₂ gas.
5. Connect the answer to the question: Based on the process of photolysis in the light-dependent reactions, the correct answer is water (H₂O), as it is the source of the oxygen gas released by plants during photosynthesis.