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
In case control study of buccal carcinoma- 
Select and explain. 
A. CA is commoner in zarda pan users than non users, B. Zarda pan is a cause of buccal CA, C. Zarda pan is associated with buccal CA, D. If use of zarda pan is stopped, number of cases will reduce
C: Zarda pan is associated with buccal CA
Answer: C: Zarda pan is associated with buccal CA 
Explanation: Case control studies often retrospective studies are a common first approach to test causal hypothesis. In recent years case control study has emerged as a permanent method of epidemiological investigation. Both exposure and outcome has occurred before the study. Study proceeds backwards from effect to cause. It uses a control or comparison group to suppo or refute an inference (refer pgno:71 park 23 rd edition)