Explanation
Business case development, including a cost-benefit analysis, will be most persuasive to management. A risk assessment may be included in the business ease, but by itself will not be as effective in gaining management support. Informing management of regulatory requirements may help gain support for initiatives, but given that more than half of all organizations are not in compliance with regulations, it is unlikely to be sufficient in many cases. Good metrics which provide assurance that initiatives are meeting organizational goals will also be useful, but are insufficient in gaining management support.

Explanation
The best way to ensure the organization's security objectives are embedded in business operations is to implement an information security governance framework. An information security governance framework is a set of policies, procedures, standards, guidelines, roles, and responsibilities that define and direct how the organization manages and measures its information security activities. An information security governance framework helps to align the information security strategy with the business strategy and the organizational culture, and to ensure that the information security objectives are consistent with the business objectives and the stakeholder expectations. An information security governance framework also helps to establish the authority, accountability, and communication channels for the information security function, and to provide the necessary resources, tools, and controls to implement and monitor the information security program. By implementing an information security governance framework, the organization can embed the information security objectives in business operations, and ensure that the information security function supports and enables the business processes and functions, rather than hinders or restricts them.
References = CISM Review Manual, 16th Edition, Chapter 1: Information Security Governance, Section:
Information Security Governance Framework, page 181; CISM Review Questions, Answers & Explanations Manual, 10th Edition, Question 75, page 702.

Explanation
During post-incident review is the best time to update the incident response plan after observing several deficiencies in the current plan while responding to a high-profile security incident. A post-incident review is a process of analyzing and evaluating the incident response activities, identifying the lessons learned, and documenting the recommendations and action items for improvement. Updating the incident response plan during post-incident review helps to ensure that the plan reflects the current best practices, addresses the gaps and weaknesses, and incorporates the feedback and suggestions from the incident response team and other stakeholders. Therefore, during post-incident review is the correct answer.
References:
* https://www.cisa.gov/sites/default/files/publications/Incident-Response-Plan-Basics_508c.pdf
* https://www.techtarget.com/searchsecurity/feature/5-critical-steps-to-creating-an-effective-incident-respon
* https://www.integrify.com/blog/posts/incident-response-plan-need-an-update/