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
Radiation is not used in: 
Select and explain. 
A. CAT scan, B. NMR, C. Digital substraction imaging, D. Thyroid scan
B: NMR
Answer: B: NMR 
Explanation: Ans. NMR