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': 'Which of the following are not non absorbable sutures : \nSelect and explain. \nA. Silk, B. Catgut, C. Metal, D. Nylon', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]