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': 'In a randomized controlled trial, the essential purpose of randomization is: \nSelect and explain. \nA. To produce double blinding., B. To decrease the follow- up period., C. To eliminate the selection bias., D. To decrease the sample size.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]