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
[{'content': 'The ultrasonic sound waves employed in ultrasound machine for medical sonography have the frequency of \nSelect and explain. \nA. 2 - 20 MHz, B. Less than 1 MHz, C. 20-20,000 Hz, D. Greater than 100 MHz', 'role': 'user'}, {'content': "Answer: A \nExplanation: Frequency refers to a characteristic of the sound that is, the number of times that conduction paicles vibrate back and foh per second. Frequency of sound waves is usually between 1 and 20 MHz in medical sonography. Hence the best answer for this question would be A. 2-20 MHz Christensen's Physics of Diagnostic Radiology, 4/E,Pg no 347", 'role': 'assistant'}]