Comprehensive and Detailed Step-by-Step Explanation:
* Reference to IIA Standards:
* Standard 2130 - Control: Internal auditors must assess whether internal controls are designed and operating effectively to mitigate identified risks.
* Standard 2200 - Engagement Planning: The objective of testing controls is to evaluate their effectiveness in achieving the desired outcomes.
* Reasoning:
* Option Ais correct because the main goal of testing controls is to determine whether they are functioning effectively to manage the identified risks and achieve control objectives.
* Option B(understanding whether a control is in place) focuses on control design but not its operational effectiveness.
* Option C(identifying patterns of errors) is related to detecting irregularities, not directly testing the control's effectiveness.
* Effectiveness of Controls:
* Internal audit testing focuses on evaluating the effectiveness and operational efficiency of controls to ensure they reduce risks to an acceptable level.