This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: NEET Jan 2020, Subject name: Pharmacology
Which of the following drugs shown in the graph below has highes potency? 
Select and explain. 
A. Drug A, B. Drug B, C. Drug C, D. Both Drug A and
A: Drug A
Answer: A: Drug A 
Explanation: Drug potency and efficacy