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
The minimum amount of fluoride required in common salt for caries reduction is 
Select and explain. 
A. 100 mg/kg, B. 90 mg/kg, C. 200 mg/kg, D. 350 mg/kg
C: 200 mg/kg
Answer: C: 200 mg/kg 
Explanation: None