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': 'Effect of chlorhexidine on long terms use can \nSelect and explain. \nA. Suppress gram +ve and gram -ve organisms, B. Suppress all microbial flora, C. Does not cause tongue discoloration, D. Has systemic effects', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]