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: Pathology
CD marker for cytotoxic T-cells? 
Select and explain. 
A. CD 4, B. CD 8, C. CD 21, D. CD 45
B: CD 8
Answer: B: CD 8 
Explanation: Ans. is 'b' i.e., CD 8