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': 'Which of the following is the most potent H2 blocker used in peptic ulcer disease \nSelect and explain. \nA. Cimetidine, B. Famotidine, C. Ranitidine, D. Nizatidine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Famotidine is the most potent H2 blocker.', 'role': 'assistant'}]