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
Navy Plaque Index was introduced by: 
Select and explain. 
A. Muhlemann, B. Ennever, C. Grossman & Fedi, D. None of the above
C: Grossman & Fedi
Answer: C: Grossman & Fedi 
Explanation: None