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: Dental
[{'content': 'The period of infancy usually refers to: \nSelect and explain. \nA. First 2 years after birth, B. First 1 year after birth, C. First 6 months after birth, D. First 3 years after birth', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]