This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': 'Active immunity is not acquired by:(1994) \nSelect and explain. \nA. Infection, B. Vaccination, C. Immunoglobulin transfer, D. Sub clinical infection', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans: c (Immunoglobulin transfer)Ref: Ananthanarayan Micro, 7lhed, p. 76 & 6th ed, p. 73', 'role': 'assistant'}]