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
The most potent stimulator of naive ? cells is: 
Select and explain. 
A. ? cell, B. Mature dendritic cells, C. Epithelial cells, D. Macrophages
B: Mature dendritic cells
Answer: B: Mature dendritic cells 
Explanation: . Mature dendritic cells