Question: how many animals died in the lake nyos tragedy
[{'answer': '3,500', 'provenance': [{'wikipedia_id': '51389757', 'title': 'Lake Nyos disaster', 'start_paragraph_id': 1, 'start_character': 99, 'end_paragraph_id': 1, 'end_character': 104, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '51389757', 'title': 'Lake Nyos disaster', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 114, 'bleu_score': 0.8970773746801091, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1500409898760224344}, 'section': 'Section::::Abstract.'}]}]