This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Assessment of Growth, Subject name: Pediatrics
[{'content': 'Which of the following-is the first sign of sexual maturity in boys? \nSelect and explain. \nA. Increase in height, B. Appearance of facial hair, C. Change in voice, D. Increase in testicular size', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) Increase in testicular sizePlease refer explanation of question 40', 'role': 'assistant'}]