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
Case control study is an example of ? 
Select and explain. 
A. Prospective study, B. Retrospective study, C. Combined retrospective and prospective study, D. Study at one point of time
B: Retrospective study
Answer: B: Retrospective study 
Explanation: Ans. is 'b' i.e., Retrospective study