<prompt> Type 4 Bismuth classification for cholangiocarcinoma:Common hepatic ductBifurcation onlyBifurcation and bilateral secondary intrahepatic ductsBifurcation and unilateral secondary intrahepatic ducts  <response>: 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. 