Question: when did the united states enter the war in europe
[{'answer': 'April 6 , 1917', 'provenance': [{'wikipedia_id': '25604889', 'title': 'United States in World War I', 'start_paragraph_id': 34, 'start_character': 54, 'end_paragraph_id': 34, 'end_character': 68, 'bleu_score': 1.0, 'section': 'Section::::War declared.\n'}]}]