After iron in the oceans took up as much oxygen as it could, what happened to th

After iron in the oceans took up as much oxygen as it could, what happened to the oxygen next?

	could not exist in the atmosphere because it was all tied up in rocks
	became readily available in the air and started accumulating in the atmosphere
	began to cycle from ocean deposits into the atmosphere and be taken up by rocks
	was released from rocks and began to cycle in Earth’s atmosphere