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: Social & Preventive Medicine
When an intervention is applied to community to evaluate its usefulness, it is termed as a trial for 
Select and explain. 
A. Effectiveness, B. Efficacy, C. Efficiency, D. Effect modification
A: Effectiveness
Answer: A: Effectiveness 
Explanation: None