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: Radiology
[{'content': 'Not a radiosensitizing agent \nSelect and explain. \nA. Metronidazole, B. Actinomycin-D, C. Hyperbaric Oxygen, D. Chlorhexidine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Chlorhexidine is Radioprotector.', 'role': 'assistant'}]