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: Physiology
[{'content': 'I cells of duodenum secrete \nSelect and explain. \nA. Secretin, B. Gastrin, C. CCK, D. Motilin', 'role': 'user'}, {'content': 'Answer: C \nExplanation: In addition to its secretion by I cells in the upper intestine, CCK is found in nerves in the distal ileum and colon.\nIt is also found in neurons in the brain, especially the cerebral cortex, and in nerves in many parts of the body.', 'role': 'assistant'}]