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 a phosphoryn indicating dentin presence 
Select and explain. 
A. Nestin, B. Arestin, C. Collagen, D. All of the above
A: Nestin
Answer: A: Nestin 
Explanation: None