In the context of COBIT 2019, design factors are essential for tailoring the governance system to the specific needs of an enterprise. These factors help shape the governance system to ensure it aligns with the enterprise's strategy, goals, and environment. When considering how to tailor the governance system to an enterprise strategy, a COBIT implementation expert would look at several design factors, one of which iscost leadership.

Detailed Explanation with References:

Cost Leadership (Option A): Cost leadership is a strategic objective where an organization aims to become the lowest-cost producer in its industry. This strategy can be a significant design factor in tailoring a governance system, as it impacts decisions on IT investments, process efficiencies, and cost management. In COBIT 2019, aligning IT governance with a cost leadership strategy involves ensuring that IT initiatives support cost reduction and operational efficiency, thereby enabling the organization to achieve competitive pricing.

Risk Optimization (Option B): While risk optimization is an essential component of IT governance, it is more related to managing and balancing risk rather than a design factor specifically tailored to enterprise strategy.

Business Transformation (Option C): Business transformation refers to major changes in an organization’s processes, systems, or structure. It is more of a broader business objective rather than a design factor used specifically in the context of tailoring the governance system to an enterprise strategy.

Value Delivery (Option D): Value delivery focuses on ensuring that IT delivers value to the business. It is a core principle of IT governance but is not typically categorized as a design factor for tailoring enterprise strategy in COBIT 2019.

Conclusion:The correct answer isA. Cost leadership. Cost leadership as a design factor directly influences how the governance system is tailored to support the enterprise strategy of achieving the lowest cost production. This alignment ensures that the governance system supports strategic goals focused on cost efficiency and competitive pricing.