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
Approximately how much time is required for progression of incipient to clinical cavitated caries on smooth surface? 
Select and explain. 
A. 10+-6 months, B. 18+-6 months, C. 25+-8 months, D. 13+-3 months
B: 18+-6 months
Answer: B: 18+-6 months 
Explanation: The time for progression from incipient caries to clinical caries (cavitation) on smooth surface is estimated to be 18 months, plus or minus 6 months.