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': "A hypertensive patient Sattu already receiving a drug 'X' to control his BP was prescribed a tricyclic antidepressant. This resulted in the abolition of the antihypertensive action of 'X'. Which of the following drug can be 'X'? \nSelect and explain. \nA. Enalapril, B. Clonidine, C. Atenolol, D. Diltiazem", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]