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 frequent cause of fracture of a root tip
during extraction of a primary molar is 
Select and explain. 
A. Ankylosis of the tooth, B. Improper use of cow horn forceps, C. Presence of supernumerary premolar, D. Root resorption between apex and bifurcation
D: Root resorption between apex and bifurcation
Answer: D: Root resorption between apex and bifurcation 
Explanation: None