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
True of case control studies - 
Select and explain. 
A. It proceeds from cause to effect, B. Odds ratio can be calculated, C. Incidence can be calculated, D. Needs many patients
B: Odds ratio can be calculated
Answer: B: Odds ratio can be calculated 
Explanation: None