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: Social & Preventive Medicine
Randomized study is done in people who are volunteer for the study. Which type of bias may occur ? 
Select and explain. 
A. Hawthorne bias, B. Berkesonian bias, C. Selection bias, D. Attention bias
C: Selection bias
Answer: C: Selection bias 
Explanation: Ans. is 'c' i.e., Selection bias