According to the PMBOK® Guide, specifically the Create WBS process, decomposition is the technique used for dividing and subdividing the project scope and project deliverables into smaller, more manageable parts.

Why Choice B is correct:

The Work Package: The lowest level of the WBS is the Work Package. By definition in PMI standards, a work package is the point at which cost and duration can be reliably estimated and managed.

Hierarchical Structure: A WBS is a deliverable-oriented hierarchical decomposition of the total scope of work. It does not include actions or dependencies (that happens in the activity list), but it provides the framework for all subsequent planning.

Control Accounts: Work packages are often grouped into control accounts for performance measurement. Without decomposing to the work package level, estimates remain high-level and prone to significant error.

Analysis of other options:

A (WBS with task sequencing): This is a common misconception. A WBS is a hierarchical decomposition of deliverables, not a chronological list of tasks. Sequencing occurs during the Develop Schedule process, not during the creation of the WBS.

C (WBS for immediate tasks only): This describes Rolling Wave Planning. While useful in some contexts, the question asks how to decompose the scope to enable detailed estimates for the project. Restricting the WBS to only " immediate " tasks would prevent the team from creating a complete baseline for the entire project scope.

D (WBS with target duration and cost): While a WBS provides the basis for these estimates, the WBS itself is a scope document. The duration and cost data are typically captured in the WBS Dictionary or the project schedule/budget, not as a label for every deliverable within the WBS graphic.

Key Concept: The Project Management Institute (PMI) emphasizes that " if it ' s not in the WBS, it ' s not in the project. " By decomposing the project to the Work Package level (Choice B), the project manager creates a " baseline " that allows for the Bottom-Up Estimating technique, which is the most accurate way to determine the project ' s total cost and duration.