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
IOC for pyonephrosis 
Select and explain. 
A. USG, B. CECT, C. IVP, D. MRI
A: USG
Answer: A: USG 
Explanation: IOC for pyonephrosis - USG.