Question: what was the cause of the black death in europe
[{'answer': 'The bacterium Yersinia pestis', 'provenance': [{'wikipedia_id': '4501', 'title': 'Black Death', 'start_paragraph_id': 1, 'start_character': 257, 'end_paragraph_id': 1, 'end_character': 287, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '4501', 'title': 'Black Death', 'start_paragraph_id': 1, 'start_character': 80, 'end_paragraph_id': 1, 'end_character': 597, 'bleu_score': 0.752481331610039, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14684607326765897796}, 'section': 'Section::::Abstract.'}]}]