Question: when did aef troops begin arriving in europe
[{'answer': 'July 5 , 1917', 'provenance': [{'wikipedia_id': '313147', 'title': 'American Expeditionary Forces', 'start_paragraph_id': 1, 'start_character': 166, 'end_paragraph_id': 1, 'end_character': 179, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '313147', 'title': 'American Expeditionary Forces', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 753, 'bleu_score': 0.9659246927162931, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8403537388140693031}, 'section': 'Section::::Abstract.'}]}]