During the Sprint Review the Product Owner introduces the functionality that is likely to be...

C. They are added to the Product Backlog and addressed throughout the next Sprints, combined with creating the business functionality in those Sprints, no matter how small that business functionality.

This is a good way because it is consistent with the Scrum principle of empiricism, which means that the Scrum Team learns and adapts based on the actual outcomes and feedback, rather than following a predefined plan12. By adding these security concerns to the Product Backlog, the Product Owner can prioritize and refine them according to the value and urgency, and communicate them to the stakeholders. By addressing them throughout the next Sprints, the Scrum Team can delivervaluable and functional increments that also meet the security requirements34. D.During the Sprint Retrospective, the Scrum Team assesses how to add these expectations to the Definition of Done so every future Increment will live up to these requirements. If needed they can work with external specialists to better understand the requirements

This is another good way because it is consistent with the Scrum value of openness, which means that the Scrum Team and the stakeholders have a clear and common understanding of the product vision, goals, progress, and risks12. By adding these expectations to the Definition of Done, the Scrum Team can ensure that every future Increment meets the quality standards and satisfies the stakeholder needs. By working with external specialists, the Scrum Team can also leverage their expertise and experience to better understand and implement the security requirements34.

References: 1: Scrum Values | Scrum.org 2: Scrum Values - Atlassian 3: Scrum Guide | Scrum Guides 4: Scrum - What is it, how it works, & how to start - Atlassian