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': 'What is the average gain in lenght in 4 years? \nSelect and explain. \nA. 25 cm, B. 50 cm, C. 75 cm, D. 100 cm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Expected height = Age (yr)\xa0× 6 + 77', 'role': 'assistant'}]