The correct answer is C. Kaizen . The CSSBB-aligned Lean material defines Kaizen as continuous improvement , usually incremental and ongoing, involving everyone in the organization. It is explicitly described as a term associated with productivity , just-in-time production , total quality control , suggestion systems , and zero defects .

That makes kaizen the best fit for improving product development, order processing, and production activities on a continuing basis. It is not limited to one event or one department; rather, it is a sustained improvement philosophy and practice. 5S is a workplace-organization method, muda means waste, and muri refers to overburden. Those concepts are important in Lean, but they are not the broad ongoing improvement method described in the question. Since the question asks for the tool or approach used to improve activities continuously over time, the correct CSSBB-based answer is Kaizen .