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: Pediatrics
[{'content': 'The following is usually the first sign of puberty in girls – \nSelect and explain. \nA. Onset of menstruation, B. Appearance of pubic hair, C. Change in voice, D. Increase in breast size', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]