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': 'During cap stage signalling in the odontogenic epithelium is done by: \nSelect and explain. \nA. Enamel knot., B. Enamel cord., C. Enamel septum., D. Enamel navel.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Recent studies have shown that enamel knot acts as a signaling center as many important growth factors are expressed by the cells of the enamel knot and thus they play an important part in determining the shape of the tooth.', 'role': 'assistant'}]