Question: in what country do the two main tributaries of the nile river join
[{'answer': 'Sudan', 'provenance': [{'wikipedia_id': '21244', 'title': 'Nile', 'start_paragraph_id': 1, 'start_character': 489, 'end_paragraph_id': 1, 'end_character': 494, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '21244', 'title': 'Nile', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 618, 'bleu_score': 0.9509503382229441, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8200042483764555215}, 'section': 'Section::::Abstract.'}]}]