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
Which of the following is the commonest cause for biliary stricture? 
Select and explain. 
A. Trauma during surgery, B. Cholangio carcinoma, C. Clonorchis infection, D. Autoimmune hepatitis
A: Trauma during surgery
Answer: A: Trauma during surgery 
Explanation: It is good to memorize the fact that procedures like ERCP can predispose to biliary strictures. Other causes include chronic inflammation secondary to gall stones, stenosis of sphincter of oddi or papillitis, cholangiohepatitis due to Opisthorchis sinesis or other parasites, cholangiocarcinoma, primary sclerosing cholangitis.