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
Berkesonian bias is a selection bias which occurs in? 
Select and explain. 
A. Community-based studies, B. Hospital-based studies, C. Laboratory-based studies, D. Natural exposure studies
B: Hospital-based studies
Answer: B: Hospital-based studies 
Explanation: Ans. is 'b' i.e., Hospital-based studies