The Great Oxygen Event marks the time, approximately 2.5 billion years ago, when ______ .
A) there was enough oxygen in the atmosphere to support a major burst of life on Earth
B) there was a massive volcanic eruption that lead to a very rapid increase in oxygen levels on Earth
C) there was significant oxygen in the atmosphere
D) there was a cataclysmic weather event that absorbed most of the oxygen in the atmosphere and locked it into iron deposits in the oceans
E) photosynthesis was clearly established and producing oxygen

Question

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The Answer of The Great Oxygen Event marks the time, approximately 2.5 billion years ago, when ______ .
A) there was enough oxygen in the atmosphere to support a major burst of life on Earth
B) there was a massive volcanic eruption that lead to a very rapid increase in oxygen levels on Earth
C) there was significant oxygen in the atmosphere
D) there was a cataclysmic weather event that absorbed most of the oxygen in the atmosphere and locked it into iron deposits in the oceans
E) photosynthesis was clearly established and producing oxygen

The Great Oxygen Event Marks the Time, Approximately 2