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': 'First appearance of tooth formation occurs in: \nSelect and explain. \nA. 6th week IU, B. 2nd week IU, C. 9th week IU, D. 4th month IU', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]