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
Which of the following property of the drug will enable it to be used in low concentration ? 
Select and explain. 
A. High affinity, B. High specificity, C. Low specificity, D. High stability
A: High affinity
Answer: A: High affinity 
Explanation: None