An external assessment of network vulnerability is a process of identifying and evaluating the weaknesses and risks that affect the security and availability of a network froman outsider's perspective. The most important factor to verify during this process is the completeness of network asset inventory, which is a list of all the devices, systems, and software that are connected to or part of the network. A complete and accurate network asset inventory can help identify the scope and boundaries of the network, the potential attack vectors and entry points, the critical assets and dependencies, and the existing security controls and gaps. Without a complete network asset inventory, an external assessment of network vulnerability may miss some important assets or vulnerabilities, leading to inaccurate or incomplete results and recommendations.
References:
1 explains what is an external vulnerability scan and why it is important to have a complete network asset inventory.
2 provides a guide on how to conduct a full network vulnerability assessment and emphasizes the importance of knowing the network assets.
3 compares internal and external vulnerability scanning and highlights the need for a comprehensive network asset inventory for both types.

The most important thing to determine next after concluding that an organization has a quality security policy is whether the policy is well understood by all employees. A security policy is a document that defines the objectives, scope, roles, responsibilities, and rules for information security within an organization. A quality security policy is one that is clear, concise, consistent, comprehensive, and aligned with business goals and requirements. However, a quality security policy is useless if it is not well understood by all employees who are expected to comply with it.Therefore, the IS auditor should assess the level of awareness and understanding of the security policy among employees and identify any gaps or issues that need to be addressed. The other options are not as important as ensuring that the security policy is well understood by all employees, as they do not directly affect the implementation and effectiveness of the security policy. References: CISA Review Manual, 27th Edition, page 317