Final answer:
The size and complexity of a project influence the plan structure, and all projects, including small ones, need planning. A work breakdown structure is often essential for project planning.
Step-by-step explanation:
The correct statement regarding project planning is that the size and complexity of the project will influence the plan structure. Every project, irrespective of its size, requires some level of planning to ensure success. While small projects might have simpler plans, they still need a structured approach to guide the project to completion.
On the other hand, large and complex projects often require detailed plans, including a work breakdown structure (WBS), which is a key tool used to break down the project into smaller, more manageable components.
It is also important to note that during the project planning phase, activities such as the development of a detailed design can consume a significant amount of time and greatly affect the project's outcome. Therefore, careful planning and a solid detailed design are crucial, as a poor detailed design can undermine an otherwise good design concept.