High employee turnover (A) poses the greatest risk because it leads to knowledge loss, operational disruptions, and potential security risks from departing employees. A constantly changing workforce can also impact compliance, training, and overall IT stability.
Other options:
Lack of customer satisfaction surveys (B) is a business issue but not a critical IT risk.
Aging staff (C) may be a long-term risk but does not have an immediate impact.
Frequent software upgrades (D) can be beneficial if managed correctly.
Reference: ISACA CISA Review Manual, IT Governance and Management of IT

The strategy that would provide the greatest assurance of system quality at implementation is delivering only the core functionality on the initial target date. This strategy can help avoid compromising the quality of the system by focusing on the essential features that meet the user needs and expectations. Delivering only the core functionality can also help reduce the scope creep, complexity, and testing efforts of the system development project.
Implementing overtime pay and bonuses for all development staff, utilizing new system development tools to improve productivity, and recruiting IS staff to expedite system development are not strategies that would provide the greatest assurance of system quality at implementation. These strategies may help speed up the system development process, but they may also introduce new risks or challenges such as burnout, learning curve, integration issues, or communication gaps. These risks or challenges may adversely affect the quality of the system.

The first step that an IS auditor should take when finding that a business impact analysis (BIA) has not been performed is to evaluate the impact on current disaster recovery capability. A BIA is a process that identifies and analyzes the potential effects of disruptions to critical business functions and processes. A BIA helps determine the recovery priorities, objectives, and strategies for the organization. Without a BIA, the disaster recovery plan may not be aligned with the business needs and expectations, and may not provide adequate protection and recovery for the most critical assets and activities. Therefore, an IS auditor should assess how the lack of a BIA affects the current disaster recovery capability and identify any gaps or risks that need to be addressed.
Performing a BIA, issuing an intermediate report to management, and conducting additional compliance testing are not the first steps that an IS auditor should take when finding that a BIA has not been performed.
These steps may be done later in the audit process, after evaluating the impact on current disaster recovery capability. Performing a BIA is not the responsibility of the IS auditor, but of the business owners and managers. Issuing an intermediate report to management may be premature without sufficient evidence and analysis. Conducting additional compliance testing may not be relevant or necessary without a clear understanding of the disaster recovery requirements and objectives.

The most important consideration when defining an operational log management strategy is understanding and meeting stakeholder requirements. This ensures that the strategy aligns with organizational needs and regulatory requirements, providing relevant and actionable information for security and compliance.
References
* ISACA CISA Review Manual 27th Edition, Page 273-274 (Log Management)

An audit report of the controls by the service provider's external auditor provides the best evidence that a third-party service provider's information security controls are effective. An external auditor is an independent and objective party that can assess the design and operating effectiveness of the service provider' s information security controls based on established standards and criteria. An external auditor can also provide an opinion on the adequacy and compliance of the service provider's information security controls, as well as recommendations for improvement.
Documentation of the service provider's security configuration controls is a source of evidence that a third- party service provider's information security controls are effective, but it is not the best evidence.
Documentation of the security configuration controls can show the settings and parameters of the service provider's information systems and networks, but it may not reflect the actual implementation and operation of the controls. Documentation of the security configuration controls may also be outdated, incomplete, or inaccurate.
An interview with the service provider's information security officer is a source of evidence that a third-party service provider's information security controls are effective, but it is not the best evidence. An interview with the information security officer can provide insights into the service provider's information security strategy, policies, and procedures, but it may not verify the actual performance and compliance of the information security controls. An interview with the information security officer may also be biased, subjective, or misleading.
A review of the service provider's policies and procedures is a source of evidence that a third-party service provider's information security controls are effective, but it is not the best evidence. A review of the policies and procedures can show the service provider's information security objectives, requirements, and guidelines, but it may not demonstrate the actual execution and enforcement of the information security controls. A review of the policies and procedures may also be insufficient, inconsistent, or outdated.
References:
* ISACA, CISA Review Manual, 27th Edition, 2019, p. 284
* ISACA, CISA Review Questions, Answers & Explanations Database - 12 Month Subscription