Question: who won the us open 2017 women's singles tennis championship
[{'answer': 'Sloane Stephens', 'provenance': [{'wikipedia_id': '54683068', 'title': "2017 US Open – Women's Singles", 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 15, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]