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': 'All of the following drugs cause tachycardia except? \nSelect and explain. \nA. Amphetamine, B. Nifedipine, C. Theophylline, D. Clonidine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Clonidine is α2 agonist and decreases the central sympathetic outflow. It decreases blood pressure as well as heart rate.', 'role': 'assistant'}]