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

Procurement Management Plan (Option D): This issue is a direct result of failing to perform a proper Make-or-Buy Analysis, which is a key tool and technique of the Plan Procurement Management process. This analysis determines whether a particular work deliverable can best be accomplished by the project team or should be purchased from outside sources. If the team had a Procurement Management Plan, they would have identified early that they lacked the expertise and time, leading to a " Buy " decision to outsource the deliverable to a vendor who could complete it in a timely manner.

Human Resource Management Plan (Option B): While this plan identifies roles, responsibilities, and required skills, it focuses on managing the personnel assigned to the project. It does not typically address the decision to acquire external products or services when internal capacity is reached.

Scope Management Plan (Option C): This plan describes how the scope will be defined and controlled. While it tells the team what needs to be done, it does not prescribe who (internal vs. external) should perform the work or how to handle the lack of internal expertise.

Risk Management Plan (Option A): This plan defines how to conduct risk management activities. While a lack of expertise is a risk, the specific operational process for deciding to outsource work to solve that problem is managed through procurement.

In the PMI framework, the Procurement Management Plan is essential for strategic resource allocation. By following this plan, a Project Manager can prevent schedule delays by identifying gaps in organizational capability and filling those gaps through external contracts before the project execution is negatively impacted.