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: Medicine
Fever blisters can occur due to? 
Select and explain. 
A. Reactivation of HSV - 1, B. Primary HSV — 1 infection, C. Varicella, D. HHV- 6
A: Reactivation of HSV - 1
Answer: A: Reactivation of HSV - 1 
Explanation: None