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: Radiology
USG is/are based on: 
Select and explain. 
A. Piezoelectric effect, B. Diamagnetic effect, C. Paramagnetic effect, D. Ferromagnetic effect
A: Piezoelectric effect
Answer: A: Piezoelectric effect 
Explanation: Ans. A. Piezoelectric effectUltrasonography:Ultrasonic image(sonographic/echographic) is based on mechanical oscillations of the crystal excited by electrical pulses (Piezoelectric effect).