This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gall Bladder & Bile Ducts, Subject name: Surgery
[{'content': 'Type 4 Bismuth classification for cholangiocarcinoma: \nSelect and explain. \nA. Common hepatic duct, B. Bifurcation only, C. Bifurcation and bilateral secondary intrahepatic ducts, D. Bifurcation and unilateral secondary intrahepatic ducts', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. (c) Bifurcation and bilateral secondary intrahepatic ductsRef: Sabiston 20th edition Page 1517As per Bismuth Corelette Classification:* Type 4 is involvement of Bilateral 2nd order Bile ducts.', 'role': 'assistant'}]