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': 'Injuries to primary teeth occur mostly at: \nSelect and explain. \nA. 6 - 12 months, B. 3 - 4 years, C. 5 - 6 years, D. 1½  - 2½ years', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Trauma to primary dentition is common, many times unnoticed as they are minor and a child who is involved in busy play or other activity may not remember minor injuries and report to parents.\nMost usual age of occurrence is 1 to 2 years as they try to stand up and walk because of lack of control on motor movements.\n28% of 5-year olds would have experienced some kind of injury to the teeth and supporting structures.\nMost injuries are luxation type as bone is resilient in primary dentition (injury is primarily to the supporting structures).\nFor injuries of permanent dentition, school age is the common age.\n20% of 12-year-olds had experienced some kind of trauma.\nMore of crown fractures compared to root fractures.\nBoys to girls ratio is said to be 2:1 but not many studies supporting this fact are available. The prevalence may be more in boys because of their physical activity.\nPrevalence of injuries is more in maxillary central incisors followed by maxillary laterals, mandibular centrals and laterals.\n\nReference: Pediatric Dentistry Principles and Practice SECOND EDITION, MS Muthu; pdf no 859', 'role': 'assistant'}]