Question: where does the blue nile river start and end
[{'answer': 'Lake Tana', 'provenance': [{'wikipedia_id': '158338', 'title': 'Blue Nile', 'start_paragraph_id': 1, 'start_character': 134, 'end_paragraph_id': 1, 'end_character': 143, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Khartoum , Sudan'}]