Question: who's the original singer of unchained melody
[{'answer': 'Todd Duncan', 'provenance': [{'wikipedia_id': '359664', 'title': 'Unchained Melody', 'start_paragraph_id': 1, 'start_character': 190, 'end_paragraph_id': 1, 'end_character': 201, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '359664', 'title': 'Unchained Melody', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 532, 'bleu_score': 0.9615098218105691, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1672702041988241558}, 'section': 'Section::::Abstract.'}]}]