Question: when is the last time duke won the ncaa tournament
[{'answer': '2015', 'provenance': [{'wikipedia_id': '8219053', 'title': "Duke Blue Devils men's basketball", 'start_paragraph_id': 11, 'start_character': 111, 'end_paragraph_id': 11, 'end_character': 115, 'bleu_score': 1.0, 'section': 'Section::::Team history.:Retired numbers.\n'}]}]