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
Nutrition for ameloblasts after 1st layer of enamel is laid is 
Select and explain. 
A. Dental sac, B. Odontoblastic process, C. REE, D. Dental papilla
A: Dental sac
Answer: A: Dental sac 
Explanation: None