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
The most common cause for gingival fistula in children is: 
Select and explain. 
A. Acute apical abscess, B. Acute periodontal abscess, C. Periapical cyst, D. Chronic apical lesion
D: Chronic apical lesion
Answer: D: Chronic apical lesion 
Explanation: None