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
Memory T cells can be identified by using the following marker - 
Select and explain. 
A. CD45 RA, B. CD45 RB, C. CD45 RC, D. CD45 RO
D: CD45 RO
Answer: D: CD45 RO 
Explanation: None