Question: which cells with in the islets of langerhans secrete insulin
[{'answer': 'beta cells', 'provenance': [{'wikipedia_id': '199453', 'title': 'Pancreatic islets', 'start_paragraph_id': 12, 'start_character': 102, 'end_paragraph_id': 12, 'end_character': 112, 'bleu_score': 1.0, 'section': 'Section::::Structure.:Microanatomy.\n'}]}, {'provenance': [{'wikipedia_id': '199453', 'title': 'Pancreatic islets', 'start_paragraph_id': 12, 'start_character': 0, 'end_paragraph_id': 12, 'end_character': 300, 'bleu_score': 0.759911015110291, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7137482834187806332}, 'section': 'Section::::Structure.:Microanatomy.\n'}]}]