This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology and Rheumatology, Subject name: Medicine
Which of the following are large, granular lymphoid cells that are mediators of antibody- dependent cellular cytotoxicity? 
Select and explain. 
A. macrophages, B. natural killer (NK) cells, C. T lymphocytes, suppressor subset, D. B lymphocytes
B: natural killer (NK) cells
Answer: B: natural killer (NK) cells 
Explanation: NK cells may be of T-cell lineage or monocyte-macrophage lineage. They appear to play an important role in surveillance mechanisms.