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 pH of a freshly prepared stannous fluoride solution is approximately 
Select and explain. 
A. 2.5, B. 4.5, C. 6.5, D. 8.5
A: 2.5
Answer: A: 2.5 
Explanation: None