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
[{'content': "Kasai's procedure is performed in \nSelect and explain. \nA. Type 4B choledochal cyst, B. Type 3B choledochal cyst, C. Type 5 choledochal cyst, D. Type 2 choledochal cyst", 'role': 'user'}, {'content': 'Answer: A \nExplanation: It is performed in in type 4b witches only extrahepatic biliary tree dilation.', 'role': 'assistant'}]