This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'Somatostatin is secreted by - \nSelect and explain. \nA. D-cell, B. A-cell, C. B-cell, D. Dl-cell', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]