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
Not a radiosensitizing agent 
Select and explain. 
A. Metronidazole, B. Actinomycin-D, C. Hyperbaric Oxygen, D. Chlorhexidine
D: Chlorhexidine
Answer: D: Chlorhexidine 
Explanation: Chlorhexidine is Radioprotector.