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: Unknown
[{'content': 'In a study in the UK, an association was found between the sale of antiarrhythmic drug and an increase in deaths due to asthma. This is an example of \nSelect and explain. \nA. Ecological study, B. Cohort study, C. Case reference study, D. Experimental study', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e. Ecological study Repeat May 08 www. ucel ac. uk. rlos/specs/rlo_observational_study. doc; http.//cancersupportivecare. com/epidemiology.html] For explanation see May 08", 'role': 'assistant'}]