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
At what age does the first tooth erupt in the oral cavity? 
Select and explain. 
A. 6 months, B. 9 months, C. 6 weeks, D. 7 weeks
A: 6 months
Answer: A: 6 months 
Explanation: None