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': 'Ectodermal cells in tooth bud are responsible for \nSelect and explain. \nA. Determination of shape of crown and root, B. Formation of periodontal ligament, C. Formation of cementum, D. Formation of pulp', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]