Earth formed about 4.5 billion years ago, and life appeared roughly 500 million years later. The first cellular forms of life, however, did not appear until about:
A{'text': '4 billion years ago, immediately after earth cooled', 'label': 'A'}
B{'text': '3 billion years ago, with the first non-cellular giants', 'label': 'B'}
C{'text': '2000 million years ago, as the first single-celled life', 'label': 'C'}
D{'text': '500 million years ago, alongside the first invertebrates', 'label': 'D'}
Answer & Solution
Correct answer: C. {'text': '2000 million years ago, as the first single-celled life', 'label': 'C'}
Per the chapter, life appeared about 4 billion years ago in the form of giant non-cellular molecules (RNA, protein, polysaccharides) around 3 billion years back, but the first cellular forms of life did not possibly originate till about 2000 million years ago.
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