The organization control environment is most effective when the controls perform as intended. The controls are the mechanisms or measures that are designed and implemented to prevent, detect, or correct the risks that may affect the achievement of the objectives. The controls perform as intended when they provide reasonable assurance that the risks are mitigated or managed to an acceptable level, and that the objectives are met or exceeded. The performance of the controls can be measured and evaluated by using key performance indicators (KPIs) and key risk indicators (KRIs). The other options are not as indicative of the effectiveness of the control environment, as they are related to the review, implementation, or efficiency of the controls, not the performance or assurance of the controls. References = Risk and Information Systems Control Study Manual, Chapter 2: IT Risk Assessment, Section 2.3: IT Control Assessment, page 69.