According to the PMBOK® Guide, the project manager should identify the source of the disagreement among the project stakeholders as the first step to facilitate the approval of project requirements. This is because identifying the source of the disagreement can help the project manager understand the root cause of the conflict, the interests and needs of the stakeholders, and the potential impact of the disagreement on the project objectives and deliverables. By identifying the source of the disagreement, the project manager can then choose an appropriate conflict resolution technique, such as compromising, collaborating, smoothing, forcing, or withdrawing, to resolve the issue and obtain the approval of the project requirements1. The other options are not the first steps to facilitate the approval of project requirements, because:

Reviewing the project charter may help the project manager clarify the project scope, objectives, and high-level requirements, but it does not address the specific source of the disagreement among the stakeholders2.

Performing a stakeholder analysis may help the project manager identify the stakeholders, their roles, expectations, influence, and communication needs, but it does not address the specific source of the disagreement among the stakeholders3.

Holding a team-building event may help the project manager improve the team morale, trust, and collaboration, but it does not address the specific source of the disagreement among the stakeholders4. References: 1: PMBOK® Guide, Sixth Edition, Chapter 9.5.2.1, Conflict Management 2: PMBOK® Guide, Sixth Edition, Chapter 4.1.3.1, Project Charter 3: PMBOK® Guide, Sixth Edition, Chapter 13.1.3.1, Stakeholder Analysis 4: PMBOK® Guide, Sixth Edition, Chapter 9.4.2.4, Team-Building Activities