The appearance of free oxygen in Earth's atmosphere led to the "Great Oxidation Event". Where did all of this oxygen come from? o A. Volcanic eruptions which spewed gases from the Earth's interior.
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B. Cyanobacteria, a mutated unicellular organism, began to release oxygen as it performed photosynthesis.
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C. The reduction of carbon dioxide which caused the Earth to freeze from pole to pole.
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D. Oxygen was released from meteors during the Late Heavy Bombardment about 3.8 billion years ago.