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
PMA index given by Schour and Massler is a method of assessing 
Select and explain. 
A. Periodontitis, B. Oral hygiene, C. Amount of calculus, D. Gingivitis
D: Gingivitis
Answer: D: Gingivitis 
Explanation: None