The purpose of a Key Control Indicator (KCI) is to measure control effectiveness. Therefore, the most important design criterion is that it demonstrates whether the control objective is being achieved.
ISACA defines:
"KCIs are metrics that measure the effectiveness of controls in achieving their intended objectives." Quantitative methods are desirable but secondary.
Hence, B is correct.
CRISC Reference: Domain 4 - Risk and Control Monitoring and Reporting, Topic: Control Performance Metrics.

A risk event is an occurrence or situation that has a negative impact on the objectives, operations, or resources of an enterprise. A data breach at the company to be acquired is a risk event for the acquiring organization, because it can affect the value, reputation, or performance of the acquisition. A risk event can also trigger other risks or consequences that may require further actions or responses. The other options are not the correct answers, because they do not describe the situation accurately. A threat event is an occurrence or situation that exploits a vulnerability or causes harm to an asset or process. An inherent risk is the risk that exists before applying any controls or treatments. A security incident is an event that violates the security policies or procedures of an enterprise. References = CRISC: Certified in Risk & Information Systems Control Sample Questions

The greatest concern for a risk practitioner when reviewing the findings of a security awareness program assessment is that the program uses non-customized training modules. Non-customized training modules are generic and may not address the specific security needs, issues, and challenges of the organization. They may also fail to engage and motivate the employees to follow the security policies and procedures, and to enhance their security knowledge and skills. The program not decreasing threat counts, not considering business impact, or being significantly revised are other possible findings, but they are not as concerning as the program using non-customized training modules. References = ISACA Certified in Risk and Information Systems Control (CRISC) Certification Exam Question and Answers, question 7; CRISC Review Manual, 6th Edition, page 202.

The most useful input to the parent company's risk practitioner when developing risk scenarios for the post-acquisition phase is the risk registers of both companies. The risk register is a document that records the details of the risks, such as their sources, causes, consequences, likelihood, impact, and responses. By reviewing the risk registers of both companies, the risk practitioner can identify the existing and potential risks that may affect the post-acquisition integration, performance, and value. The risk management framework, the IT balanced scorecard, and the most recent internal audit findings are other possible inputs, but they are not as useful as the risk registers. References = ISACA Certified in Risk and Information Systems Control (CRISC) Certification Exam Question and Answers, question 11; CRISC Review Manual, 6th Edition, page 144.

In this context, the internal IT team acts as data custodians. Data custodians are responsible for the safe custody, transport, storage, and overall safeguarding of data. They ensure that data is properly maintained and that access controls are in place, but they do not make decisions about data usage-that responsibility lies with data owners.
Reference:ISACA CRISC Review Manual, 7th Edition, Chapter 4: Information Technology and Security, Section: Data Management Roles and Responsibilities.