Final answer:
The work breakdown structure should be broken down until each task is manageable and measurable, representing option D. This ensures that each subproject can be effectively controlled and its progress can be assessed, leading to a well-organized and successful overall project.
Step-by-step explanation:
To define a work breakdown structure (WBS) is to iteratively divide a project into smaller pieces or subprojects. This process, often referred to as subdividing or decomposition, continues until the project manager identifies work packages that are sufficiently detailed and scoped. The ideal work packages should be both manageable and measurable, which corresponds to option D. 'Manageable' means that each task is small enough to be assigned and controlled effectively, while 'measurable' implies the ability to assess progress and performance against the project objectives. Work that is simple may still be too large or not precisely quantifiable, and complexity doesn't necessarily imply a clear path for measurement or management. Therefore, when breaking down a project into smaller subprojects, we want to ensure that each component is refined enough to be executed on effectively, with clear objectives and success criteria. This detailed level of planning contributes to the overall project's organization and helps teams move toward successful completion.