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: Surgery
Aminopeptidase is elevated in obstruction of ? 
Select and explain. 
A. Ureter, B. Urethra, C. CBD, D. Bladder
C: CBD
Answer: C: CBD 
Explanation: Ans. is 'c' i.e., CBD