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
Gnarled enamel is seen in: 
Select and explain. 
A. Proximal surface of tooth, B. Cervical region of tooth, C. Cusp tips of tooth, D. All of the above
C: Cusp tips of tooth
Answer: C: Cusp tips of tooth 
Explanation: None