This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sedative-Hypnotics and Parkinsonism, Subject name: Pharmacology
Dose response curve of diazepam was produced alone and in the presence of flumazenil. Which of the following is true regarding the effect of flumazenil on the graph given below 
Select and explain. 
A. Decrease in Potency and no effect on efficacy, B. Decrease in Potency and decrease in efficacy, C. No effect on Potency and no effect on efficacy, D. No effect on Potency and decrease in efficacy
A: Decrease in Potency and no effect on efficacy
Answer: A: Decrease in Potency and no effect on efficacy 
Explanation: Competitive antagonist decrease potency with no change in efficacy. The effect of antagonist (flumazenil) can be overcome by increasing the concentration of agonist(diazepam)