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
Who introduced patient hygiene performance index (PHP Index) 
Select and explain. 
A. Podshadly & Haley, B. Green & Vermilion, C. Gruebell, D. Quigley & Hein
A: Podshadly & Haley
Answer: A: Podshadly & Haley 
Explanation: None