The correct answer is D. kanban . The CSSBB source defines kanban as a method of material control intended to provide product with short lead times while reducing inventory and controlling replenishment through pull signals. It describes the system as one in which parts are supplied to the next operation based on a kanban instruction , rather than being sent whenever upstream operations happen to finish.

That fits this question exactly. The problem is that subassemblies are being pushed into final assembly as they are completed, creating confusion and disorder. A kanban system would convert that push behavior into a pull system , so final assembly receives material when it is actually needed and in the right quantity. Standard work helps define the best method, 5S improves workplace organization, and poka-yoke helps prevent errors, but none of those is primarily a material-replenishment control method. Since the root issue is uncontrolled flow of containers into final assembly, the Lean tool designed to address it is kanban . Therefore, the verified answer is D .