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': 'Immunity by vaccination is \nSelect and explain. \nA. Active natural, B. Passive natural, C. Active acquired, D. Passive acquired', 'role': 'user'}, {'content': "Answer: C \nExplanation: Active immunity occurs as a result of infection or by specific immunization and is usually associated with the presence of antibodies or cells having a specific action on the microorganism or on its toxin. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 109", 'role': 'assistant'}]