Question: when did us first send troops to afghanistan
[{'answer': '7 October 2001', 'provenance': [{'wikipedia_id': '19666611', 'title': 'War in Afghanistan (2001–present)', 'start_paragraph_id': 1, 'start_character': 231, 'end_paragraph_id': 1, 'end_character': 245, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '19666611', 'title': 'War in Afghanistan (2001–present)', 'start_paragraph_id': 2, 'start_character': 203, 'end_paragraph_id': 2, 'end_character': 1455, 'bleu_score': 0.5650417600480141, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 164486216169065930}, 'section': 'Section::::Abstract.'}]}]