This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Radiology
Investigation of choice for choledocolithiasis is 
Select and explain. 
A. CT, B. USG, C. PET scan, D. HIDA scan
A: CT
Answer: A: CT 
Explanation: (Ref: Grainger and Allison&;s diagnostic radiology 6th edition, chapter 32)