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: Radiology
Frostburg's reverse 3 sign is seen in – 
Select and explain. 
A. Periampullary carcinoma, B. Annular pancreatic carcinoma, C. Carcinoma head of pancreas, D. All
C: Carcinoma head of pancreas
Answer: C: Carcinoma head of pancreas 
Explanation: Reversed '3' sign of frost berg  → Carcinoma head of pancreas.
Double duct sign → Periampullary carcinoma.
"Beaded appearance" of biliary ducts → Primary sclerosing cholangitis.