This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Medicine
[{'content': 'All of the following drugs are commonly used in regimens against H. pylori except - \nSelect and explain. \nA. Oxytetracycline, B. Amoxicillin, C. Bismuth subcitrate, D. Omeprazole', 'role': 'user'}, {'content': 'Answer: A \nExplanation: <p>Davidson&;s principles and practice of medicine 22nd edition. *Drugs used amoxicillin,clarithromycin,metronidazole for 7 days. *Amoxicillin ,omeprazole,bismuth subcitrate and tetracycline.</p >', 'role': 'assistant'}]