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
Cap stage contains the following transitory structure: 
Select and explain. 
A. Enamel matrix., B. Stratum intermedium., C. Cervical loop., D. Enamel knot,Enamel cord,Enamel niche.
D: Enamel knot,Enamel cord,Enamel niche.
Answer: D: Enamel knot,Enamel cord,Enamel niche. 
Explanation: None