This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
[{'content': 'In a population of 5000, on 1st January, total cases of myopia were 500. Till 31st December, 90 new cases were found. Calculate the incidence of myopia per 100 \nSelect and explain. \nA. 1.8, B. 2, C. 5, D. 18', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Incidence = Number of new cases of a specified disease during a given time period x 100 Population at risk during that periodPopulation at risk = 5000-500= 4500Incidence of myopia during the year in the population would be - 90 x 100 = 2 per 100 4500', 'role': 'assistant'}]