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
Lip bumper is used for: 
Select and explain. 
A. Mouth breathing, B. Nail biting, C. For lip biting & hyperactive rnentalis, D. All of the above
C: For lip biting & hyperactive rnentalis
Answer: C: For lip biting & hyperactive rnentalis 
Explanation: Lip Bumper
Lip bumper is an appliance that makes use of the tonicity of the lip. The lip trap and excessive lip activity can be helped with a lip bumper  which prevents lip pressure on the lower incisor; their labial position gets normalised with tongue pressure. The lost arch length can also be gained with this method.
Key Concept: 
The lip trap and excessive lip activity can be helped with a lip bumper which prevents lip pressure on the lower incisor.
Reference: Orthodontics: Diagnosis and Management of Malocclusion and
Dentofacial Deformities 3rd ed Om P. Kharbanda pdf no 736