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 a randomized controlled trial, the essential purpose of randomization is: 
Select and explain. 
A. To produce double blinding., B. To decrease the follow- up period., C. To eliminate the selection bias., D. To decrease the sample size.
C: To eliminate the selection bias.
Answer: C: To eliminate the selection bias. 
Explanation: None