A scientist had discovered 2 drugs, drug X and Y. Both drugs provide pain relief at 20 mg dose. However, the pain relief intensity varies between the two. On a scale of 1-10 (with 10 being the highest pain relief), drug X provides pain relief up to a scale of 9, whereas Drug Y's pain relief effect is only 5. What would be the correct statement regarding Drug X and Y?
A. Drug X is more potent than Drug Y
B. Drug Y is more potent than Drug X
C. Drug X has more efficacy than Drug Y
D. Drug Y has more efficacy than Drug X