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: Forensic Medicine
[{'content': 'Four carpal bones are present at what age? \nSelect and explain. \nA. 3 years, B. 4 years, C. 5 years, D. 6 years', 'role': 'user'}, {'content': "Answer: B \nExplanation: 4 years REF: Parikh 6' edition page 2.9 Between 2 to 6 years, the number of carpal bones present on X ray represents the approximate age in years, as for example, four carpal bones -- 4 years.", 'role': 'assistant'}]