According to IIA guidance, the focus of a review of controls to prevent fraud should be on the effectiveness rather than the efficiency of the controls. Effectiveness pertains to whether the controls adequately mitigate fraud risks and prevent fraudulent activities, while efficiency focuses on the performance and cost-effectiveness of the controls, which is not the primary concern in preventing fraud. This makes statement A false in the context of IIA guidance.
Reference:
IIA Standards: 1220.A1 - Due Professional Care
IIA Practice Guide: Fraud Prevention and Detection in an Automated World