This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bile duct, Subject name: Surgery
In a patient of cholangitis, surgical intervention was performed. In post-operative period, on 10th day this investigation was performed. What is the name of this investigation? 
Select and explain. 
A. ERCP, B. MRCP, C. T-tube cholangiogram, D. PTC
C: T-tube cholangiogram
Answer: C: T-tube cholangiogram 
Explanation: The investigation is T-tube cholangiogram.