Step 1: Understanding Oxygen Production in Photosynthesis.
In photosynthesis, oxygen is produced during the light reactions when water is split by Photosystem II, releasing oxygen, protons, and electrons.
Step 2: Analyzing the Options.
- (A) Correct. Oxygen is released when water is split during the light reactions in Photosystem II.
- (B) Incorrect. Photosystem I does not produce oxygen; it is involved in the production of NADPH.
- (C) Incorrect. Oxygen is produced in Photosystem II, not Photosystem I.
- (D) Incorrect. Oxygen production is not only in the presence of light but specifically in the light reactions.
Step 3: Conclusion.
Thus, the correct answer is (A).