This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunity, Subject name: Pathology
Null cells constitute what percentage of peripheral lymphocytes? 
Select and explain. 
A. 0-1, B. 5-Feb, C. 10-May, D. 15-20
C: 10-May
Answer: C: 10-May 
Explanation: Ans. (c) 5-10(Ref: Robbins 9th/pg 192; 8th/pg 188)Natural Killer Cells or Null cells constitute 5% to 10% of peripheral lymphocytes QAs NK cells neither have B nor T-cell markers, hence also called Null CellsNK cells destroy irreversibly stressed, virus-infected cells & tumor cells without prior exposure