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: Microbiology
[{'content': 'NK cells activity is enhanced by - \nSelect and explain. \nA. IL-1, B. TNF, C. IL-2, D. TGP-β', 'role': 'user'}, {'content': 'Answer: C \nExplanation: IL-2 acts as a growth factor for N K cells.', 'role': 'assistant'}]