This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
[{'content': 'Edmonston strain is - \nSelect and explain. \nA. Hepatitis-B, B. Measles, C. Mumps, D. Rubella', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In measels, active immunization is by vaccine used Edmonston strain REF:<\\p> MICROBIOLOGY ANANTHA NARAYANAN NINTH EDITION PAGE.513', 'role': 'assistant'}]