This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
What is the most appropriate for diagnosis of CBD stones 
Select and explain. 
A. Ultrasonography, B. ERCP, C. OCG, D. IV cholangiography
B: ERCP
Answer: B: ERCP 
Explanation: USG : first test, can document GB stones and estimate the CBD diameter A dilated bile duct (>8mm in diameter) in a patient with gallstones, jaundice and biliary pain is highly suggestive of choledocholithiasis MRCP : Provides excellent anatomic detail with sensitivity and specificity of 95 %and 98 %, respectively, for CBD stones ERCP : Diagnostic and therapeutic test of choice for patients with suspected CBD stones Ref: Sabiston 20th edition Pgno :1494