This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal tract, Subject name: Pharmacology
[{'content': 'Which of the following drugs is not used for H. pylon treatment? \nSelect and explain. \nA. Oxytetracycline, B. Bismuth compounds, C. clarithromycin, D. Omeprazole', 'role': 'user'}, {'content': 'Answer: A \nExplanation: H. pylori is a gram negative bacillus uniquely adapted to survival in the hostile environment of stomach. Antimicrobials that have been found clinically effective against H. pylori are: amoxicillin, clarithromycin, tetracycline and metronidazole/ tinidazole. (Essentials of pharmavology KD Tripathy,6th edition,pg no.637)', 'role': 'assistant'}]