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
Apart from T & B lymphocytes, the other class of lymphocytes is - 
Select and explain. 
A. Macrophages, B. Astrocytes, C. NK cells, D. Langerhans cells
C: NK cells
Answer: C: NK cells 
Explanation: Lymphoid cells

The cells of the lymphoid system are lymphocytes.


On the basis of function and surface markers, there are two major types of lymphocytes-


T- cells
B- cells


When circulating lymphocytes are classified by their surface markers into T and B cells, about 5-10 percent of cells are found to lack features of either type they are called null cells/Large granular lymphocytes.
Large granular lymphocytes include:

           - Natural killer cells (N.K Cells)
           - Antibody-dependent cytotoxic cells/killer cells (ADCC).
           - Lymphokine-activated killer cells (LAK cells).