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: Dental
[{'content': 'Metronidazole is NOT effective in the treatment of \nSelect and explain. \nA. Amoebiasis, B. Infections due to Bacteroides fragilis, C. Infections due to Pneumocystis carinii, D. Acute necrotizing ulcerative gingivitis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]