Which of the following is a procurement document?

A Work Breakdown Structure is a scope management tool that hierarchically decomposes project deliverables and has no role in engaging or soliciting external vendors.

A project charter is a project initiation document that formally authorizes the project and designates the project manager, not a document used in the procurement process.

A vision document captures high-level product goals and stakeholder needs during requirements gathering and is not associated with procurement or vendor selection.

An Invitation for Bid (IFB) is a standard procurement solicitation document used when the buyer has fully specified requirements and selection will be based primarily on price. It is part of the conduct procurements process in PMBOK and belongs alongside other procurement documents such as Requests for Proposal (RFP) and Requests for Quotation (RFQ), all of which are used to engage external sellers.