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: Pharmacology
Drugs with high affinity can be used in : 
Select and explain. 
A. High concentration., B. Low concentration., C. Moderate concentration., D. None.
B: Low concentration.
Answer: B: Low concentration. 
Explanation: Affinity is the ability of a drug to combine with the receptor.