Question: who is the best selling country artist of all time
[{'answer': 'Elvis Presley', 'provenance': [{'wikipedia_id': '1291598', 'title': 'List of best-selling music artists', 'start_paragraph_id': 1, 'start_character': 890, 'end_paragraph_id': 1, 'end_character': 903, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]