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
[{'content': 'Most difficult criterion on establishing a causal association in the aetiology of a disease is - \nSelect and explain. \nA. Temporality, B. Strength of association, C. Specificity of association, D. Biological plausibility', 'role': 'user'}, {'content': "Answer: C \nExplanation: Park's textbook of preventive and social medicine 23rd edition. *Specificity is the most difficult criterion to establish not only in chronic disease but also in acute diseases and conditions.", 'role': 'assistant'}]