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: Social & Preventive Medicine
[{'content': "Strain used for BCG vaccine - \nSelect and explain. \nA. Edmonston Zagreb strain, B. Oka strain, C. 'Danish' 1331, D. RA 27/3strain", 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Danish 1331", 'role': 'assistant'}]