This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Classification, Coho Study, Subject name: Social & Preventive Medicine
[{'content': 'Best epidemiological study to know Causality is: \nSelect and explain. \nA. Coho study, B. Case control study, C. Cross sectional study, D. Ecological study', 'role': 'user'}, {'content': "Answer: A \nExplanation: Temporal association Implies 'cause precedes effect' or 'effect follows cause'. Is 'most impoant criterion' of casual association. Is ' best established by a coho study' (Especially concurrent coho study) as coho study is forward study.", 'role': 'assistant'}]