According to the PMBOK® Guide (Project Management Body of Knowledge), specifically within the Project Scope Management knowledge area and the Plan Scope Management process:

Plan Scope Management (Option C): This is the process of creating a scope management plan that documents how the project and product scope will be defined, validated, and controlled. The key benefit of this process is that it provides guidance and direction on how scope will be managed throughout the project. It explicitly outlines the procedures for preparing the scope statement, creating the WBS, formalizing the acceptance of completed deliverables (Validate Scope), and processing change requests to the scope baseline (Control Scope).

Define Scope (Option A): This is the process of developing a detailed description of the project and product. Its primary output is the Project Scope Statement. While it defines what is in scope, it does not define the administrative process for how that scope will be validated or controlled.

Develop Project Management Plan (Option B): This is a high-level integration process that defines, prepares, and coordinates all plan components. While the Scope Management Plan eventually becomes a subsidiary part of this larger plan, the specific act of defining scope validation and control happens within the Plan Scope Management process.

Plan Quality Management (Option D): This process identifies quality requirements and/or standards for the project and its deliverables, and documents how the project will demonstrate compliance. It focuses on correctness and " fit for use " rather than the formal acceptance and boundary management of the scope.

In the PMI framework, the Scope Management Plan acts as a roadmap. By defining how the project scope will be validated (through the Validate Scope process) and controlled (through the Control Scope process), the Project Manager ensures that there is a clear, pre-approved methodology for handling scope creep and securing formal sign-off from the customer.