Question: what was the cause of the deepwater horizon oil spill
[{'answer': 'Deepwater Horizon drilling rig explosion', 'provenance': [{'wikipedia_id': '27242394', 'title': 'Deepwater Horizon explosion', 'start_paragraph_id': 1, 'start_character': 5, 'end_paragraph_id': 1, 'end_character': 46, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '27242394', 'title': 'Deepwater Horizon explosion', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 686, 'bleu_score': 0.9106679819523871, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6480996408208495114}, 'section': 'Section::::Abstract.'}]}]