Final answer:
A kanban card is used in manufacturing systems to signal that more parts or work is needed from the preceding station, ensuring a continuous production process.
Step-by-step explanation:
A kanban card is a tool used in lean manufacturing and just-in-time production systems to control inventory and signal the need for new supplies or work. It is closely associated with the Toyota Production System. When considering your example of a factory where cars are built and the use of a conveyor belt to move the car through various assembly stations, the correct function of a kanban card in such a context is to signal that work is needed from the preceding station. Whenever inventory at a station reaches a certain minimum level, a kanban card is sent to the previous station to indicate that more parts or work is required to ensure a continuous operation. Therefore, the correct answer to your question would be D) work is needed from the preceding station.