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': 'Asbestos filter used for absolute sterility? \nSelect and explain. \nA. HP : PYR, B. HP : EK, C. HP : EKS, D. HP : MK', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]