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
Killer cells & helper cells are pa of - 
Select and explain. 
A. B cells, B. T cells, C. Monocytes, D. Macrophages
B: T cells
Answer: B: T cells 
Explanation: The category of effector T cell is a broad one that includes various T cell types that actively respond to a stimulus, such as co-stimulation. This includes helper, killer, regulatory, and potentially other T cell types. Reff: Ananthanarayanan & Panikers textbook of microbiology 9th edition pg: 135