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
Vertical extension of the enamel knot known as: 
Select and explain. 
A. Enamel Knot., B. Enamel navel., C. Enamel cord., D. Enamel septum.
C: Enamel cord.
Answer: C: Enamel cord. 
Explanation: None