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
Which of the following is not an ecto-mesenchymal derivative? 
Select and explain. 
A. Dentin, B. Cementum, C. Pulp, D. Enamel
D: Enamel
Answer: D: Enamel 
Explanation: None