According to the PMBOK® Guide, specifically the Develop Project Charter process, the primary function of the project charter is to formally authorize the project and provide the project manager with the authority to act.

Formal Authority: The charter is signed by the project initiator or sponsor. By signing it, the organization officially recognizes the project ' s existence and, most importantly, empowers the project manager to use organizational resources (such as people, equipment, and budget) to achieve the project objectives.

Establishing a Partnership: It creates a formal link between the performing organization and the requesting organization. Before the charter is signed, a project manager may be " assigned, " but they do not have the formal power to make financial commitments or direct staff until the charter is approved.

High-Level Alignment: The charter provides the " why " of the project. It outlines the high-level objectives, success criteria, and constraints, ensuring that the project manager and the stakeholders are aligned before detailed planning begins.

Analysis of other options:

Option A: Detailing requirements for project tasks occurs much later in the planning phase during the Collect Requirements and Define Scope processes. The charter only contains high-level requirements.

Option C: Listing all tasks is the purpose of the Work Breakdown Structure (WBS) and the Activity List, which are created during the planning phase. The charter is too high-level to include individual tasks.

Option D: The Business Case is actually an input to the project charter. It is usually developed by a business analyst or sponsor before the project starts to justify the investment. The charter uses the business case as a foundation but does not " develop " it.

Per PMI standards, the most critical goal of the Project Charter is the formalization of the project and the empowerment of the project manager, granting them the legal and organizational standing to lead the project team toward its goals.