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
Rapid progressive juvenile periodontitis is seen usually at which age? 
Select and explain. 
A. 6-10 years, B. 10-20 years, C. 30-40 years, D. At any age
B: 10-20 years
Answer: B: 10-20 years 
Explanation: None