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': 'Congenitally missing teeth are the result of failure in which stage of development? \nSelect and explain. \nA. Initiation, B. Morphodifferentiation, C. Apposition, D. Calcification', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Initiation and proliferation are the only possibilities for congenitally absent teeth, the bud and cap stages, respectively. In the histodifferentiation stage, the teeth are present; failure in this stage results in structural abnormalities of the enamel and dentin. Failure in the morphodifferentiation stage results in size and shape abnormalities.', 'role': 'assistant'}]