The risk register typically provides the best overview of an organization's audit universe when developing a long-term audit plan. It identifies and categorizes risks across various business areas, helping auditors prioritize their focus based on the significance and potential impact of different risks to the organization.

Enterprise architecture (EA) provides the best overview of an organization's audit universe when developing a long-term audit plan because it encompasses all aspects of the organization's structure, processes, and technology infrastructure, allowing auditors to prioritize areas for audit effectively.

D. Enterprise architecture (EA). Enterprise architecture (EA) provides a comprehensive view of an organization's structure, processes, systems, and technology infrastructure. It encompasses various domains, including business architecture, information architecture, application architecture, and technology architecture. By examining the enterprise architecture, auditors can gain insights into the organization's overall structure, operations, dependencies, and key systems. This understanding helps in identifying audit areas, assessing risks, and developing a strategic and holistic audit plan that aligns with the organization's objectives and priorities.

D. Enterprise architecture (EA) Enterprise architecture provides a holistic view of the organization’s strategy, business processes, information systems, and technologies. It helps in understanding the interdependencies between these elements and their alignment with the organization’s objectives. This comprehensive view is crucial when developing a long-term audit plan as it helps in identifying potential areas of risk and control across the organization.