B is correct, Project plan definition: A high-level plan showing the major products of the project and when, how, and at what cost they will be delivered.

16.4.7: "Before committing to major expenditure on the project, the timescale and resource requirements must be established. This information is held in the project plan and is needed so that the business case can be refined and the project board can control the project." 16.4.8: "The outline business case produced during starting up a project needs to be updated to reflect the estimated time and costs, as determined by the project plan, and the aggregated risks from the updated risk register." Also note that the initiation stage plan is created in the Starting up a project process.

A Project Plan provides the Business Case with an estimate of planned costs of the project, and it identifies the management stages and other major control points that will be used. The Project Plan is used by the Project Board as a baseline against which to monitor project Progress , so the Project Board can be asking “how are we doing compared to the original project plan?”