Question: who proposed the idea that cells can be classified in one of three major groups
[{'answer': 'Carl Woese et al.', 'provenance': [{'wikipedia_id': '164897', 'title': 'Three-domain system', 'start_paragraph_id': 1, 'start_character': 69, 'end_paragraph_id': 1, 'end_character': 86, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '164897', 'title': 'Three-domain system', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 833, 'bleu_score': 0.984188478234951, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16032607350770268359}, 'section': 'Section::::Abstract.'}]}]