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
Best caries activity test used for field study is 
Select and explain. 
A. Lactobacillus count test, B. Streptococcus mutans, C. Snyder's test, D. Saliva /tongue blade method
D: Saliva /tongue blade method
Answer: D: Saliva /tongue blade method 
Explanation: None