The Heavy Oxygen Isotope (¹⁸O) Could Be Provided to Plants

The heavy oxygen isotope (¹⁸O) could be provided to plants either in the CO₂ or in H₂O or in both. Today, we know from experimental results that O₂ released from chloroplasts comes from H₂O and not from CO₂. Which of the following experimental results would show conclusively that O₂ is released from H₂O and not CO₂?

A) When heavy oxygen is part of water given to the plant, the plant produces heavy O₂.
B) When heavy oxygen is part of both water and CO₂ given to the plant, the plant produces heavy O₂.
C) When no heavy oxygen is part of water given to the plant, the plant produces no heavy O₂.
D) When no heavy oxygen is part of CO₂ given to the plant, the plant produces no heavy O₂.
E) When heavy oxygen is part of CO₂ given to the plant, the plant produces heavy O₂.