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: Psychiatry
[{'content': 'Fluoxetine is a potent reuptake blocker of this substance? \nSelect and explain. \nA. Morphine, B. Serotonin, C. Norepinephrine, D. Cholecystokinin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Serotonin', 'role': 'assistant'}]