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: Pathology
If the distance between the tip of tongue and insertion of lingual frenum is 6 mm, then it will be: 
Select and explain. 
A. Mild ankyloglossia, B. Moderate ankyloglossia, C. Severe ankyloglossia, D. Complete ankyloglossia
C: Severe ankyloglossia
Answer: C: Severe ankyloglossia 
Explanation: Class 1 - Mild ankyloglossia - 12-15 mm
Class 2 - Moderate ankyloglossia - 8-11 mm
Class 3 - Severe ankyloglossia - 4-7 mm
Class 4 - Complete ankyloglossia - 0-3 mm.