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
Sonic system runs at 
Select and explain. 
A. 2-3 KHZ, B. 25-30 KHz, C. 15-20 KHz, D. None of the above
A: 2-3 KHZ
Answer: A: 2-3 KHZ 
Explanation: None