According to the PMBOK Guide, specifically within the sections on Project Management and Strategy, projects are the primary means by which an organization achieves its strategic goals. Organizational planning dictates how projects are selected and prioritized.

Strategic Alignment: Projects are typically authorized as a result of one or more strategic considerations. The Strategic Plan serves as the highest-level roadmap for the organization, and any potential project must be evaluated against how well it aligns with these long-term goals.

Prioritization Factors: When an organization conducts its planning, it looks at several variables to decide which projects to fund and initiate:

Risk: The potential for negative impacts or failure.

Funding: The availability of capital and expected Return on Investment (ROI).

Strategic Goals: Market demand, technological advance, legal requirements, or social need as defined in the Strategic Plan.

Portfolio Management: This is the level where organizational planning most directly impacts projects. Portfolio managers use the Strategic Plan to ensure that the 'right' work is being done to move the company toward its vision.

Analysis of other choices:

Choice A (Budget plan): While funding is a constraint mentioned in the question, the 'Budget Plan' is usually a subset of the broader strategic and operational plans. It tells you if you can afford a project, but the Strategic Plan tells you why you should do it.

Choice B (Resource plan): Resource planning (human and physical) is a critical operational component, but prioritization is driven by the value the project brings to the organization's strategy, not just the availability of staff.

Choice C (Scope plan): Scope planning is project-specific. It defines what the project will do once it has already been selected. It does not drive the organizational-level prioritization process.