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: Pathology
In which of the following conditions " Onion Skin" fibrosis of bileduct is seen 
Select and explain. 
A. Ulcerative collitis, B. Primary sclerosing cholangitis, C. Primary biliary cirrhosis, D. Cholangiocarcinoma
B: Primary sclerosing cholangitis
Answer: B: Primary sclerosing cholangitis 
Explanation: Concentric periductal fibrosis is known as onion skin fibrosis and is classical of Primary sclerosing cholangitis.