Final answer:
The Strategic Plan is crucial in a project portfolio process as it sets a high-level direction and aligns projects with the organization's overall goals, distinct from the roles of a project manager, the project charter, or the portfolio manager.
Step-by-step explanation:
In a project portfolio process, the main purpose of the d) Strategic Plan is to establish and articulate a strategic direction for those projects spanning the internal or external boundaries of the organization. Unlike project managers (a), who oversee the specifics of individual projects, or project charters (b), which formalize the objectives and constraints of a specific project, the strategic plan provides a high-level vision that aligns project goals with the overall objectives of the organization. Portfolio Managers (c), while they oversee groupings of projects to ensure alignment with strategic objectives, still operate within the framework provided by the strategic plan.