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': "According to Boyd's classification, when the pain continues but the patient can still walk with effort is: \nSelect and explain. \nA. Grade 1, B. Grade 2, C. Grade 3, D. Grade 4", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Boyd’s classification:\n\nGrade I: pain disappears, if the patient continues to walk\nGrade II: pain continues, but the patient can still walk with effort\nGrade III: pain compels the patient to take rest.', 'role': 'assistant'}]