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
[{'content': 'Vertical extension of the enamel knot known as: \nSelect and explain. \nA. Enamel Knot., B. Enamel navel., C. Enamel cord., D. Enamel septum.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]