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
The most difficult criterion to establish Causal association in etiology of a disease is- 
Select and explain. 
A. Temporality, B. Strength of association, C. Specificity of association, D. Biological plausibility
C: Specificity of association
Answer: C: Specificity of association 
Explanation: Specificity of association means that the disease is caused by a paicular risk factor. It is difficult criterion to establish, as it is difficult to rule out the same outcomes by other exposures. Other Hill's criteria of causal association/ Surgeon general's criteria include: Temporality Consistency Strength Biological plausibility Coherence Dose response relationship Cessation of exposure.