* A risk register is a document that records and tracks the information about the risks that may affect the organization's objectives, such as the risk description, category, source, cause, impact, probability, status, owner, response, etc.
* When updating the risk register after a risk assessment, the most important information to include is the likelihood and impact of the risk scenario. This means that the risk register should reflect the current or updated estimates of the probability and consequence of the risk scenario, based on the risk analysis and evaluation methods and criteria.
* The likelihood and impact of the risk scenario helps to determine the risk level and priority, select the most appropriate risk response, allocate the resources and budget for risk management, and monitor and report the risk performance and outcomes.
* The other options are not the most important information to include when updating the risk register after a risk assessment. They are either secondary or not essential for risk management.
The references for this answer are:
* Risk IT Framework, page 29
* Information Technology & Security, page 23
* Risk Scenarios Starter Pack, page 21

The most comprehensive resource for prioritizing the implementation of information systems controls is the risk register. The risk register is a document that records the identified risks, their analysis, and their responses.
The risk register provides a holistic and systematic view of the risk profile and the risk treatment of the organization. The risk register can help to prioritize the implementation of information systems controls by providing the information on the likelihood, impact, and exposure of the risks, the effectiveness and efficiency of the controls, and the gaps or issues of the control environment. The other options are not as comprehensive as the risk register, as they are related to the specific aspects or components of the information systems controls, not the overall assessment and evaluation of the information systems controls. References = Risk and Information Systems Control Study Manual, Chapter 2: IT Risk Assessment, Section 2.4: IT Risk Response, page 87.

Section: Volume D