Ace the PfMP Challenge 2026 – Elevate Your Project Portfolio Mastery!

The correct choice highlights that milestone tasks are specifically defined as significant points in a project that do not consume time; therefore, they typically have a duration of zero. In project management, milestones serve as key indicators or checkpoints and are essential for tracking the progress of the project.

Milestone tasks, by definition, are often the culmination of various phases or deliverables within a project. They are not defined by the allocation of labor resources, as they do not represent ongoing work but rather essential points of completion. Therefore, to be considered a milestone, a task should indeed be a lowest-level task with zero duration. This characteristic is crucial because assigning a duration to a milestone could create confusion in reporting and tracking the project's timeline.

Having only one labor resource attached to a milestone is also a standard practice, as it emphasizes that the milestone represents a singular achievement rather than a collaborative task. This helps clarify accountability and ensures that the milestone's significance is not diluted by the involvement of multiple resources. Overall, the correct answer encapsulates the essential criteria for what constitutes a milestone task in project management.