In long-term projects executed in stages, it's essential to continuously evaluate whether the intended business value is being realized as the project progresses. Monitoring benefits at project milestones allows the project manager and stakeholders to assess if the project is still aligned with the business objectives and delivering the intended value.

According to the PMBOK® Guide – Seventh Edition (Principle 1 and Principle 7: Focus on Value), the project manager must ensure that the project delivers value continuously and not just at the end. Benefits realization is measured at key points (e.g., stage gates or milestones) to confirm alignment with the business plan.

Option A (ETC) refers to the cost/time remaining and doesn't directly assess realized business value.

Option B (throughput analysis) is a Lean metric, not directly tied to business value unless explicitly defined.

Option C (NPS) is a customer satisfaction metric and may not always correlate with monetized value.