The best approach for determining the overall IT risk appetite of an organization when business units use different methods for managing IT risks is to prioritize the organization's IT risk scenarios. IT risk appetite is the amount and type of IT risk that an organization is willing to accept in pursuit of its objectives. IT risk scenarios are hypothetical situations that describe the potential impact of IT risk events on the organization's objectives, processes, and resources. By prioritizing the organization's IT risk scenarios, the IS auditor can identify the most significant IT risks that affect the organization as a whole, and align them with the organization's strategic goals, values, and culture. Prioritizing the organization's IT risk scenarios can also help to communicate and monitor the IT risk appetite across the organization, and facilitate consistent and informed decision making. The other approaches (A, B and D) are not effective for determining the overall IT risk appetite of an organization, as they do not consider the impact and likelihood of IT risks on the organization's objectives, nor do they account for the diversity and complexity of IT risks across different business units. References: CISA Review Manual (Digital Version), Chapter 2: Governance and Management of Information Technology, Section 2.3: Information Technology Risk Management