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
[{'content': 'When a drug is evaluated for its usefulness in controlled conditions, it is termed as a trial signifying: \nSelect and explain. \nA. Efficacy, B. Effectiveness, C. Efficiency, D. Effect modification', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Efficacy is the maximum effect of a drug regardless of\xa0dose. It is determined under controlled conditions in\xa0clinical trials.\nEffectiveness is the response of a drug in Clinical set\xa0up. It may not yield the maximum benefit.', 'role': 'assistant'}]