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': 'Not true regarding NK cells - \nSelect and explain. \nA. Active against malignant cells, B. Inactive MHC antigen for killing microorganisms, C. First line defense against viral infections, D. No prior sensitization required', 'role': 'user'}, {'content': "Answer: B \nExplanation: NK cell's cytotoxicity is not antibody dependent or MHC restricted :NK cellsNatural killer cells Reff: Anantharayan & Panikers textbook f microbiology 9th edition pg:137", 'role': 'assistant'}]