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
Piezo electric scaler has a wavelength of: 
Select and explain. 
A. 6000-9000 Hz, B. 9000-12000 Hz, C. 2000-30000 Hz, D. 20000-45000 Hz
D: 20000-45000 Hz
Answer: D: 20000-45000 Hz 
Explanation: None