Question: who is the head of state in nigeria
[{'answer': 'Muhammadu Buhari', 'provenance': [{'wikipedia_id': '24110210', 'title': 'List of heads of state of Nigeria', 'start_paragraph_id': 14, 'start_character': 14, 'end_paragraph_id': 14, 'end_character': 30, 'bleu_score': 1.0, 'section': 'Section::::Military rule (1983–1993).\n'}]}]