This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacodynamics, Subject name: Pharmacology
Which is the most appropriate definition of Spare receptors ? 
Select and explain. 
A. The receptors which remain unoccupied even after drug produces maximal response, B. The receptors for binding of Inverse agonist, C. The receptors that produce adverse drug effects, D. The receptors that are unable produce maximum response
A: The receptors which remain unoccupied even after drug produces maximal response
Answer: A: The receptors which remain unoccupied even after drug produces maximal response 
Explanation: Spare receptors : Receptors that are still left unoccupied , even with a concentration of agonist that produces maximal biological response. e.g Myocardial cells are said to contain a large propoion of spare b adrenoceptors.