This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fundamentals in Radiology, Subject name: Radiology
Frequency of sound waves used in USG - 
Select and explain. 
A. < 1000 Hz, B. > 5000 Hz, C. > 10000 Hz, D. > 20000 Hz
D: > 20000 Hz
Answer: D: > 20000 Hz 
Explanation: Frequency of sound waves used in usg is >20000Hz.