Comprehensive and Detailed 200 to 250 words of Explanation From Exact Extract of project-programme-and-portfolio-management of 5th Edition MSP:

The Assurance Theme in MSP 5th Edition emphasizes that assurance should be risk-based and proportional. While independence is a success factor, the framework also recognizes that "internal" assurance—conducted by individuals with the right skills who are not the direct project managers—is a valid and necessary part of the assurance landscape.

In this scenario, the Programme Office Lead (who is a senior member of the portfolio office) is tasked with the health check. Option A is the correct answer because, within the MSP 5th Edition guidance, the Programme Office is responsible for providing standards, support, and "second-line" assurance. Even if the health check was not in the original Assurance Plan, MSP is designed to be flexible; an SRO has the authority to request ad-hoc assurance if they perceive a risk or need to understand the status of a transformation. The Programme Office Lead possesses the specialized knowledge of MSP processes and organizational standards to identify areas of concern. While an external auditor (third-line) offers more independence, the internal lead provides a cost-effective and immediate source of expertise to meet the SRO's needs. The key is that the person conducting the check must have the requisite skills to evaluate the programme against its defined governance and objectives, which a senior portfolio office member is expected to possess.