Question: which gas most likely was not part of earth's early atmosphere
[{'answer': 'Oxygen', 'provenance': [{'wikipedia_id': '23092516', 'title': 'Atmospheric methane', 'start_paragraph_id': 3, 'start_character': 366, 'end_paragraph_id': 3, 'end_character': 372, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '23092516', 'title': 'Atmospheric methane', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 587, 'bleu_score': 0.978606533029418, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1713962847819784767}, 'section': 'Section::::Abstract.'}]}]