Question: when does the us open tennis start in 2017
[{'answer': 'August 28', 'provenance': [{'wikipedia_id': '51884449', 'title': '2017 US Open (tennis)', 'start_paragraph_id': 26, 'start_character': 100, 'end_paragraph_id': 26, 'end_character': 109, 'bleu_score': 1.0, 'section': 'Section::::Singles seeds.\n'}]}]