According to the PMBOK® Guide, specifically within the Perform Integrated Change Control process, the Change Control Board (CCB) is a formally chartered group responsible for reviewing, evaluating, approving, delaying, or rejecting changes to the project.

Hierarchy of Approval: While the CCB has the authority to approve or reject changes within the scope of the project ' s baselines, certain changes may exceed the CCB ' s authority or have significant impacts on the project ' s strategic goals, funding, or contractual obligations.

Final Authorization: In many organizational frameworks, after the CCB provides its technical and impact-based approval, the customer (especially in external projects) or the sponsor (the person providing the financial resources) must provide the final sign-off. This is particularly true if the change requires additional funding from management reserves or alters the high-level requirements defined in the Project Charter.

Communication of Results: Once all required approvals are obtained, the Change Log is updated, and the project manager ensures that the changes are incorporated into the Project Management Plan and communicated to all stakeholders.

Comparison with other options:

A. Functional managers: While they may be consulted during the impact analysis (especially regarding resource availability), they do not typically sit above the CCB or the Sponsor for final project-level change approval.

B. Business partners: While they are stakeholders, they generally do not have formal approval authority over project change requests unless specifically stated in a joint venture agreement.

D. Subject matter experts (SMEs): SMEs provide the technical expertise needed to evaluate the change request, but they do not have the formal authority to approve it.