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
Permanent retainer is sometimes needed in cases of: 
Select and explain. 
A. Severe malocclusion, B. Anterior cross bite, C. Severe rotations, D. Transposition
C: Severe rotations
Answer: C: Severe rotations 
Explanation: None