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': 'The "Relative risk" of 0.25 indicates- \nSelect and explain. \nA. 75% reduction of the incidence rate in the exposed individuals compared with the unexposed, B. 25% increase in the incidence rate in the exposed individuals compared with the unexposed, C. 2.5 % times higher risk in the exposed individuals compared with the unexposed, D. 75% risk increase in the exposed individuals compared with the unexposed', 'role': 'user'}, {'content': "Answer: A \nExplanation: Defined as the ratio between the incidence among exposed persons and incidence among non exposed. A typical case-control study does not provide incidence rates from which relative risks can be calculated directly because there is no appropriate denominator or population at risk to calculate these risks Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 86", 'role': 'assistant'}]