💡 The four-level model for reviewing application controls within the business process method consists of the following levels: 1. Mega Process – The highest level, representing broad organizational functions (e.g., "Supply Chain Management"). 2. Major Process – A significant process within a mega process (e.g., "Procurement Process"). 3. Subprocess – A detailed step within a major process (e.g., "Vendor Selection"). 4. Activity – The most granular level, representing specific tasks performed within a subprocess (e.g., "Approving a Purchase Order"). Level 4 (Activity Level) focuses on the detailed actions performed within a subprocess. This level is critical for reviewing application controls, as it involves specific system functions such as data entry validation, access controls, and automated approval workflows.