The project manager should first meet with the stakeholder to better understand their expectations and update the stakeholder engagement plan. The stakeholder engagement plan is a component of the project management plan that identifies the strategies and actions required to promote productive involvement of stakeholders in project decisions and execution1. By meeting with the stakeholder, the project manager can identify the stakeholder's information needs, communication preferences, and level of interest and influence on the project. This will help the project manager to tailor the periodic reports and other communication methods to meet the stakeholder's expectations and increase their satisfaction and support for the project2.
Option A is not the best answer because adding the stakeholder details into the periodic reports and updating the project management plan is a possible action to take after meeting with the stakeholder and understanding their expectations. It is not the first thing to do.
Option B is not the best answer because inviting the stakeholder to all future project review meetings and updating the project management plan is also a possible action to take after meeting with the stakeholder and understanding their expectations. It is not the first thing to do.
Option C is not the best answer because updating the project management plan with the new information and informing all of the relevant stakeholders is a general and vague action that does not address the specific issue of the stakeholder's complaint. It is not the first thing to do. References: 1: PMBOK Guide, 7th Edition, Section 13.1.3.1, Stakeholder Engagement Plan 2: PMBOK Guide, 7th Edition, Section 13.2.2.4, Communication Requirements Analysis