This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
When a drug is evaluated for its usefulness in controlled conditions, it is termed as a trial signifying: 
Select and explain. 
A. Efficacy, B. Effectiveness, C. Efficiency, D. Effect modification
A: Efficacy
Answer: A: Efficacy 
Explanation: Efficacy is the maximum effect of a drug regardless of dose. It is determined under controlled conditions in clinical trials.
Effectiveness is the response of a drug in Clinical set up. It may not yield the maximum benefit.