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': 'Who introduced patient hygiene performance index (PHP Index) \nSelect and explain. \nA. Podshadly & Haley, B. Green & Vermilion, C. Gruebell, D. Quigley & Hein', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]