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
A child has 12 permanent and 12 deciduous teeth, what could be his age: 
Select and explain. 
A. 9 years, B. 11 years., C. 5 years., D. 15 years.
A: 9 years
Answer: A: 9 years 
Explanation: None