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
[{'content': 'Study of alcohol intake for 20 years and occuring of liver disease is a type of \nSelect and explain. \nA. Cohort study, B. Case control study, C. Ecological study, D. RCT', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]