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': 'A 6 months old child does not have any tooth in mouth. Normally by what maximum age first tooth should erupt. \nSelect and explain. \nA. 10 to 11 months, B. 6 to 8 months, C. 14 to 16 months, D. All of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In primary dentition the variation of eruption has a range of 4-5 months, Since first tooth erupts at an age of 6 months then a variation of 4-5 months can be considered normal.', 'role': 'assistant'}]