According to the PMBOK Guide, the project manager should manage stakeholder expectations and communicate any changes that affect the project scope, schedule, cost, or quality. The project manager should also collaborate with the product owner, who is responsible for defining and prioritizing the product backlog, to ensure that the stakeholder's needs are met. The product owner can assess the value and urgency of the new requirement and decide whether it should be added to the current sprint or deferred to a later release. The other options are either too passive, too risky, or too disruptive for the project. References: PMBOK Guide, 6th edition, page 49-50, section 2.1.3; page 135-136, section 4.2.3.1; page 540-541, section 13.3.2.4.