PK0-005 Project Life Cycle Practice Question
During the Planning phase, a project manager is building the work breakdown structure (WBS) for a construction project. Which TWO characteristics must the WBS satisfy? (Choose two.)
⚠ Common exam trap
The trap here is treating the WBS as a task list or org chart, when it is a deliverable-oriented hierarchy governed by the 100 percent rule.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Work packages are decomposed to a level where cost and duration can be reliably estimated.
A sound WBS follows the 100 percent rule and decomposes deliverables into work packages detailed enough for reliable estimating and control. Organizing by reporting structure, mandating vendor execution, or forcing one-day durations are not WBS requirements and would undermine the deliverable-oriented structure needed for scope management.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Work packages are decomposed to a level where cost and duration can be reliably estimated.
Why this is correct
A valid WBS decomposes deliverables into work packages that are small enough for accurate estimating, scheduling, and control. If a work package is too broad, estimates become unreliable and tracking progress is difficult. This characteristic supports the planning goal of creating a manageable, measurable scope baseline that the team can execute and monitor effectively.
- ✗
Every element is organized by the organizational reporting structure rather than by deliverable.
Why it's wrong here
The WBS is deliverable-oriented, not organized around the reporting hierarchy. Mapping work to departments is handled by a responsibility assignment matrix such as RACI, which is separate from the WBS. Structuring the WBS by reporting lines would obscure scope and make it harder to verify that all deliverables are covered.
- ✓
The 100 percent rule is applied so all project work is captured and nothing extraneous is included.
Why this is correct
The 100 percent rule states that the WBS must include all work required to complete the project and nothing more. This ensures the scope baseline is complete and prevents scope creep from undocumented work. It also means the sum of child-level work equals the parent deliverable, providing a reliable basis for estimating and control.
- ✗
The WBS is decomposed until every activity has a duration of exactly one day.
Why it's wrong here
There is no fixed rule that work packages must be one day in duration. Decomposition continues only until estimates and control are practical, which varies by project size and risk. Imposing a one-day rule would create unnecessary administrative overhead and could fragment work into unmanageable pieces.
- ✗
Each work package is assigned to at least one external vendor for execution.
Why it's wrong here
There is no requirement that work packages be outsourced. Internal team members routinely perform work packages, and forcing vendor assignment would distort make-or-buy decisions. Procurement choices are made separately based on capability, cost, and risk, not as a structural rule of the WBS.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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