Applying the theory of constraints would affect the improvement strategy because TOC focuses on identifying the system constraint, exploiting it, subordinating other activities to it, and elevating the bottleneck to improve overall throughput. In Six Sigma Improve Phase work, this directly influences how the team chooses and sequences solutions. Rather than optimizing isolated process steps, the team uses TOC thinking to target the constraint that most limits system performance. This shapes the overall strategy for improvement by changing where resources are applied, what changes are prioritized, and how success is defined. Updated FMEA, DOE plans, and benchmarking may still support the project, but they are not the primary deliverables most directly shaped by TOC logic. The major effect is on the chosen path for process improvement and the design of interventions across the value stream. For Black Belts, integrating TOC prevents local optimization and helps ensure that the implemented solution improves end-to-end system performance. Therefore, the correct answer is C, Improvement strategy, because the theory of constraints most strongly changes how the team designs and prioritizes its improvement actions.