This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pharmacology
[{'content': 'Which of the following is a potassium channel opener? \nSelect and explain. \nA. Nicorandil, B. Ranolazine, C. Ivabradine, D. Nitroprusside', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (A) Nicorandil(Ref: Harrison 12th/1862)Nicorandil is the agent that causes coronary dilation by activating myocardial ATP sensitive K+ channels. Inaddition it possesses NO releasing property; to which tolerance does not develop.', 'role': 'assistant'}]