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: Pharmacology
[{'content': 'Sudden withdrawal of which of the following drugs could result in serious adverse cardiovascular changes in a patient taking the drug over a long time: \nSelect and explain. \nA. Phenelzine (MAO inhibitor), B. Enalapril (ACE inhibitor), C. Clonidine (α2 agonist), D. Fluoxetine (serotonin reuptake inhibitor)', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]