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': 'In patients with breast cancer, chest wall involvement means  involvement of any one of the following structures except: \nSelect and explain. \nA. Serratus anterior, B. Pectoralis, C. Intercoastal muscles, D. Rib', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]