Question: who traced the course of the niger in africa
[{'answer': 'Mungo Park', 'provenance': [{'wikipedia_id': '232700', 'title': 'Mungo Park (explorer)', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 10, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]