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: Physiology
Immunologicaly active cells are: 
Select and explain. 
A. Plasma cells, B. MAST cells, C. Eosinophils, D. R.B.C s
A: Plasma cells
Answer: A: Plasma cells 
Explanation: None