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
Cumulative index is: 
Select and explain. 
A. Russet's periodontal index, B. Ramjford's periodontal index, C. PMA (Massler and Schlour), D. Gingival index (Loe and Silness)
C: PMA (Massler and Schlour)
Answer: C: PMA (Massler and Schlour) 
Explanation: None