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
Adolescent starts at the age of ? 
Select and explain. 
A. 7 years, B. 10 years, C. 14 years, D. 17 years
B: 10 years
Answer: B: 10 years 
Explanation: None