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
60 yrs old, air in biliary tree, colicky abdominal pain hyper-peristaltic abdominal sounds diagnosis - 
Select and explain. 
A. Gall stone ileus, B. Hemobilia, C. Cholangitis, D. Pneumobilia
A: Gall stone ileus
Answer: A: Gall stone ileus 
Explanation: Answer- A. Gall stone ileusPresence in air in biliary tract along with sign of intestinal obstruction is characteristic of gall stone ileus.