This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Cause to effect progression is seen in all EXCEPT- 
Select and explain. 
A. Case control study, B. Ecological study, C. Coho study, D. Randomized control trail
A: Case control study
Answer: A: Case control study 
Explanation: a case control study is always employed in such diseases where an exposure and outcome had already occurred.it is a retrospective kind of study in which the study always progresses from effect to cause. ref:park&;s textbook of preventive and social medicine,22nd edition,pg no 71