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
In the pre-school stage what % of the children show thumb-sucking 
Select and explain. 
A. Less than 10%, B. 10-20%, C. More than 50%, D. all children
C: More than 50%
Answer: C: More than 50% 
Explanation: None