This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Efficacy of the drug refers to 
Select and explain. 
A. Affinity of the drug to bind to the receptor, B. Affinity of the drug that binds to the receptor and activates it, C. Dose that required to to produce response, D. Maximum response a drug can produce
D: Maximum response a drug can produce
Answer: D: Maximum response a drug can produce 
Explanation: Efficacy means effectiveness, i.e. the ability of something, e.g. a medicine, to produce the results you want Ref-KDT 7/e p54