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: Anatomy
[{'content': 'Spiral valve is seen in which - \nSelect and explain. \nA. Neck of gall bladder, B. Cystic duct, C. Colon, D. Pylorus', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The mucons membrane of the cystic duct forms a series of 5-12 crescentic folds, arranged spirally to form the so called spiral valve of Heister. This is not a true valve.', 'role': 'assistant'}]