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
Which is the most sensitive test for ureteric stone? 
Select and explain. 
A. USG, B. Non contrast CT scan, C. Intravenous pyelogram, D. X- ray
B: Non contrast CT scan
Answer: B: Non contrast CT scan 
Explanation: Where available, a non-contrast helical CT scan with 5 millimeters (0.20 in) sections is the diagnostic modality of choice in the radiographic evaluation of suspected nephrolithiasis. All stones are detectable on CT scans except very rare stones composed of ceain drug residues in the urine, such as from indinavir.