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
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 trial
A: Case control study
Answer: A: Case control study 
Explanation: Ans. is 'a' i.e., Case control study o Case-control study proceeds backward from effect to cause, i.e. disease has already occured in subjects. o All other studies proceeds forward from cause to effect, i.e. disease has not occured in subjects.