Question: when was the last election held in nigeria
[{'answer': '28 and 29 March 2015', 'provenance': [{'wikipedia_id': '43707932', 'title': '2015 Nigerian general election', 'start_paragraph_id': 1, 'start_character': 42, 'end_paragraph_id': 1, 'end_character': 62, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '43707932', 'title': '2015 Nigerian general election', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 310, 'bleu_score': 0.96188712955549, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2726994367020719886}, 'section': 'Section::::Abstract.'}]}]