The only thing that can be provided by asymmetric encryption is nonrepudiation. Nonrepudiation is the ability to prove that a message or transaction was originated or authorized by a specific party. Asymmetric encryption uses a pair of keys: a public key and a private key. The public key can be shared with anyone, while the private key is kept secret by the owner. If a message is encrypted with the sender's private key, only the sender's public key can decrypt it. This proves that the message was sent by the sender and not by anyone else. This is called digital signature and it provides nonrepudiation. Asymmetric encryption can also provide information privacy by encrypting a message with the receiver's public key, so that only the receiver's private key can decrypt it. However, information privacy can also be provided by symmetric encryption, which uses a single key to encrypt and decrypt messages. References:
* CISA Review Manual (Digital Version), Chapter 5, Section 5.21
* CISA Online Review Course, Domain 3, Module 2, Lesson 12

The most important thing for the IS auditor to determine in a post-implementation review of a recently purchased system is whether the user requirements were met. User requirements are the specifications and expectations of the users of the system, such as the features, functions, performance, quality, and security of the system. User requirements are usually defined and documented in the early stages of the system acquisition process, such as in the request for proposal (RFP) or the contract. User requirements are also used as the basis for testing and evaluating the system before and after implementation.
Determining whether the user requirements were met can help the IS auditor assess whether the system is fit for purpose and delivers value and benefits to the users and the organization. Determining whether the user requirements were met can also help the IS auditor identify any gaps, issues, or problems with the system that may affect its functionality, usability, or reliability. Determining whether the user requirements were met can also help the IS auditor provide feedback and recommendations for improvement or enhancement of the system.
Stakeholder expectations were identified is not the most important thing for the IS auditor to determine in a post-implementation review of a recently purchased system, but rather a prerequisite or input for it.
Stakeholder expectations are the needs and wants of the various parties who have an interest or influence in the system, such as users, managers, customers, suppliers, regulators, or auditors. Stakeholder expectations are usually identified and analyzed in the initial stages of the system acquisition process, such as in the feasibility study or the business case. Stakeholder expectations are also used as inputs for defining and prioritizing the user requirements.
Vendor product offered a viable solution is not the most important thing for the IS auditor to determine in a post-implementation review of a recently purchased system, but rather an outcome or result of it. Vendor product is the system that is provided by an external supplier or service provider to meet the user requirements. Vendor product offered a viable solution means that the vendor product satisfied or exceeded the user requirements and delivered value and benefits to the users and organization. Vendor product offered a viable solution can be determined by comparing and evaluating the user requirements and the vendor product performance and quality.
Test scenarios reflected operating activities is not the most important thing for the IS auditor to determine in a post-implementation review of a recently purchased system, but rather a factor or criterion for it. Test scenarios are sets of conditions or situations that are used to test and verify whether the system meets the user requirements. Test scenarios reflected operating activities means that test scenarios simulated or replicated real-world scenarios that occur during normal operations of business processes or functions that use or depend on the system. Test scenarios reflected operating activities can help ensure that test results are valid, reliable, and relevant.
References:
* Post Implementation Review: How to conduct and its Benefits 1
* Post-implementation reviews - Department of Prime Minister and Cabinet 2
* How To Conduct A Post Implementation Audit of Your Recently Installed System 3

KPIs are not clearly defined is the most concerning finding for an IS auditor, because it implies that the third- party vendor does not have a clear understanding of what constitutes success or failure in their performance.
This can lead to inaccurate or misleading reporting, poor decision making, and lack of accountability. KPIs should be SMART (specific, measurable, achievable, relevant, and time-bound) and aligned with the business objectives and expectations of the stakeholders12. References: 1: CISA Review Manual (Digital Version), Chapter 5, Section 5.3.2 2: CISA Online Review Course, Module 5, Lesson 3

A contingency facility is a backup site that can be used to resume business operations in the event of a disaster or disruption at the primary site. The most important consideration for a contingency facility is that it is located a sufficient distance away from the primary site, so that it is not affected by the same event that caused the disruption. For example, if the primary site is damaged by a fire, flood, earthquake, or terrorist attack, the contingency facility should be in a different geographic area that is unlikely to experience the same hazard. This way, the organization can continue to provide its services and products to its customers and stakeholders without interruption.
The other options are not as important as the location of the contingency facility. The badge access controls, the number of business assets, and the identifiability of the sites are secondary factors that may affect the security and efficiency of the contingency facility, but they are not essential for its functionality. Therefore, option C is the correct answer.
References:
The Importance of Contingency Planning
WHO guidance for contingency planning