This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Introduction to Radiology, Subject name: Radiology
Radio frequency waves are used in which of the following imaging modality? 
Select and explain. 
A. PET scan, B. MRI, C. CT, D. Ultrasound
B: MRI
Answer: B: MRI 
Explanation: *MRI is based on Gyromagnetic propey of protons. *MRI uses Non-ionizing radiation i.e. Radiofrequency waves. *USG is also Non-ionizing but uses UltraSound waves. *PET scan uses Gamma rays. *CT scan uses X rays.