The Rack at My Assembly Station That Holds Rear View

Multiple Choice

The rack at my assembly station that holds rear view mirrors is empty, so a runner wheels it away and replaces it with a new rack, fully populated with rear view mirrors. This production factoid illustrates which of the following principles of the Toyota Production System?

A) All work must be specified as to content.
B) Every customer-supplier connection must be direct and unambiguous.
C) The pathway for every service and product must be direct.
D) Any improvements to the system must be made in accordance with the scientific method.