This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
In echocardiography pulses of of ultrasonic waves are admitted at a frequency of 
Select and explain. 
A. 1 megahez, B. 2 megahez, C. 20 Hez, D. 2000 Hez
B: 2 megahez
Answer: B: 2 megahez 
Explanation: In echocardiography pulses of ultrasonic waves at a frequency of 2.25 megahez are admitted from a transducer that also functions as a receiver as a receiver to detect waves reflected back from various pas of the hea. Ref:page no 347 Textbook of physiology Volume 1 AK Jain 7th edition