Question: when did the us acquire the virgin islands
[{'answer': '1917', 'provenance': [{'wikipedia_id': '2748206', 'title': 'History of the United States Virgin Islands', 'start_paragraph_id': 7, 'start_character': 67, 'end_paragraph_id': 7, 'end_character': 71, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]