Which best describes the origin of life according to the data?
(A) Life required an environment with atmospheric oxygen and any type of nucleic acids.
(B) Life required an environment with atmospheric carbon dioxide, but not atmospheric oxygen.
(C) Life required an environment with self-replicating nucleic acids that can take on many shapes.
(D) Life required an environment with nucleic acids and proteins, but not atmospheric oxygen.

It is difficult to determine exactly how life began. Answer the following questions as if the following data had been collected billions of years ago.

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Atmospheric carbon dioxide Atmospheric oxygen RNA Protein DNA Life 4 billion years ago Present 3.5 billion years ago Present 3.25 billion years ago Present Absent Absent Absent Absent Absent Absent Present Absent Present Present Absent Absent Present Present Present 3 billion years ago Present Present Present Present Present Present