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
Blinding can be done to eliminate which type of bias: 
Select and explain. 
A. Berksonian, B. Recall, C. Confounding, D. Interviewers
D: Interviewers
Answer: D: Interviewers 
Explanation: None