The best method to identify unnecessary controls is reviewing system functionalities associated with business processes, because this can help to determine whether the controls are relevant, effective, and efficient for the current business needs and objectives. System functionalities are the capabilities and features of IT systems that support the execution and performance of business processes. Business processes are the set of interrelated activities that transform inputs into outputs to deliver value to customers or stakeholders. By reviewing system functionalities associated with business processes, an organization can assess whether the controls are aligned with the process requirements, expectations, and outcomes, and whether they add value or create waste. The review can also identify any gaps, overlaps, redundancies, or conflicts among the controls, and any changes or improvements that are needed to optimize the controls. The other options are less effective methods to identify unnecessary controls. Evaluating the impact of removing existing controls can help to measure the benefits and costs of the controls, but it does not address the root causes or sources of the unnecessary controls. Evaluating existing controls against audit requirements can help to ensure compliance and assurance, but it does not consider the business context or purpose of the controls. Monitoring existing key risk indicators (KRIs) can help to measure the level and impact of risks, but it does not evaluate the suitability or adequacy of the controls. References = Surveying Staff to Identify Unnecessary Internal Controls - Methodology and Results