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': 'Helper T-cells are primarily involved in - \nSelect and explain. \nA. Cell mediated immunity, B. Killing virus infected cells, C. Killing tumor cells, D. Involved in type II hypersensitivity', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e.. Cell mediated immunity", 'role': 'assistant'}]