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: Unknown
[{'content': 'The Earliest sign of male puberty is : \nSelect and explain. \nA. Pubic hair, B. Axillary hair, C. Hoarseness of voice, D. Testicular enlargement', 'role': 'user'}, {'content': 'Answer: D \nExplanation: In boys, first visible sign of puberty and hallmark of SMR2 is testicular enlargement, beginning as early as 9½ years. This is followed by penile growth during SMR3. Peak growth occurs when testis volumes reach approximately 9-10 cm3 during SMR4. Under the influence of LH and testosterone, and prostate enlarge. The left testis normally is lower than the right. Some degree of breast hypertrophy, typically bilateral, occurs in 40-65% of boys during SMR2-3 due to a relative excess of estrogenic stimulation\nIn girls, the first visible sign of puberty and the hallmark of SMR2 is the appearance of breast buds, between 8 and 12 years of age. Menses typically begins 2-2½ years later, during SMR3-4 (median age, 12 years; normal range, 9-16 years), around the peak height velocity. Less obvious changes include enlargement of the ovaries, uterus, labia, and clitoris, and thickening of the endometrium and vaginal mucosa', 'role': 'assistant'}]