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': 'Which is not a first-generation chemical plaque control agent? \nSelect and explain. \nA. Phenol, B. Antibiotics, C. CHX, D. Sanguinarine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Chemical plaque control agents\nFirst generation:\n\nEg: Antibiotics, phenol quaternary ammonium compounds and sanguinarine.\n\nSecond generation:\n\nBisbiguanides (Chlorhexidine)\n\nThird generation\n\nDelmopinol', 'role': 'assistant'}]