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
Primary herpetic gingivostomatitis usually occurs: 
Select and explain. 
A. Prior to age 10, B. Between ages 13 to 30, C. At the onset of the menstrual period, D. During menopause
A: Prior to age 10
Answer: A: Prior to age 10 
Explanation: None