Final answer:
Defining what leads to successful completion of a project planning activity falls under 'Scope definition.' This step involves the creation of a detailed project plan that outlines specific goals, deliverables, and constraints, shaping the final detailed design crucial for project success.
Step-by-step explanation:
Under project planning activities, defining what leads to successful completion is primarily involved in b. Scope definition. The scope definition process involves determining and documenting the specific project goals, deliverables, tasks, costs, and deadlines. It encompasses understanding the project requirements from the stakeholder's perspective, which eventually leads to a clear detailed design that is crucial for a project's success.
The development of a detailed design is an extensive part of a product design project, where the most time is spent to transform a design concept into a tangible plan. During the problem definition step, a meticulous analysis of customer needs, market competition, regulations, and design constraints is conducted to establish a comprehensive understanding of the project's scope and the resources at hand. This detailed understanding is crucial and is expressed as a problem statement along with criteria and constraints.