Explanation
Updating details within the risk register is the next step for the information security manager to do after senior management has accepted the risk of noncompliance with a new regulation because it records and communicates the risk status, impact, and response strategy to the relevant stakeholders. Reporting the decision to the compliance officer is not the next step, but rather a possible subsequent step that involves informing and consulting with the compliance officer about the risk acceptance and its implications.
Reassessing the organization's risk tolerance is not the next step, but rather a possible subsequent step that involves reviewing and adjusting the organization's risk appetite and thresholds based on the risk acceptance and its implications. Assessing the impact of the regulation is not the next step, but rather a previous step that involves analyzing and evaluating the potential consequences and likelihood of noncompliance with the regulation. References:
https://www.isaca.org/resources/isaca-journal/issues/2016/volume-6/how-to-measure-the-effectiveness-of-inform
https://www.isaca.org/resources/isaca-journal/issues/2017/volume-3/how-to-measure-the-effectiveness-of-your-i

Explanation
Conducting a business impact analysis (BIA) is the first step when creating an organization's disaster recovery plan (DRP) because it helps to identify and prioritize the critical business functions or processes that need to be restored after a disruption, and determine their recovery time objectives (RTOs) and recovery point objectives (RPOs)2. Identifying the response and recovery teams is not the first step, but rather a subsequent step that involves assigning roles and responsibilities for executing the DRP. Reviewing the communications plan is not the first step, but rather a subsequent step that involves defining the communication channels and protocols for notifying and updating the stakeholders during and after a disruption. Developing response and recovery strategies is not the first step, but rather a subsequent step that involves selecting and implementing the appropriate solutions and procedures for restoring the critical business functions or processes. References:
2
https://www.isaca.org/resources/isaca-journal/issues/2018/volume-3/business-impact-analysis-bia-and-disaster-r

Explanation
Human resources (HR) is the most critical function when initiating the removal of system access for terminated employees because it is responsible for notifying the relevant parties, such as information security, help desk, and legal, of the employee's termination status and date. HR also ensures that the employee's exit process is completed and documented, and that the employee returns any company-owned devices or assets.
HR also coordinates with the employee's manager and team to ensure a smooth transition of work and responsibilities.