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
Causal association factors can be revealed by - 
Select and explain. 
A. Case control study, B. Cohort study, C. Cross sectional study, D. Experimental study
A: Case control study
Answer: A: Case control study 
Explanation: None