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
A child resorts to lip biting habit without primary involvement of mentalis muscle, the differential diagnosis is: 
Select and explain. 
A. Learned habit, B. Lack of parental care, C. Class II div I malocclusion, D. Patient is suffering from xerostomia resulting in cracked lips
C: Class II div I malocclusion
Answer: C: Class II div I malocclusion 
Explanation: An important consideration is the necessity for making a differential diagnosis before attempting to break the lip habits. If there is class II div 1 malocclusion or an excessive overjet problem, the abnormal lip activity may be purely compensatory or adaptive to the dentoalveolar morphology. Abnormal lip activity is almost always associated with Class II div 1 malocclusion and open bite problems, and the elimination of the malocclusion usually restores normal muscle function.