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': "Commonest complication of Colles' fracture is: \nSelect and explain. \nA. Nonunion, B. Malunion, C. Vascular injury, D. Sudeck's osteodystrophy", 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Malunion', 'role': 'assistant'}]