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': 'Direction of case control study \nSelect and explain. \nA. Direction of study is reverse but time is forward, B. Direction of study is forward and time is also forward, C. Direction of study is forward and time is reverse, D. Direction of study is reverse and time is also reverse', 'role': 'user'}, {'content': "Answer: A \nExplanation: Case-control study has 3 distinct features: Both exposure and outcome have occurred before the sta of the study The study proceeds backward from effect to cause It uses a control or comparison group to suppo or refute an inference Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 79", 'role': 'assistant'}]